Questioning a Part's Authenticity Before You Install It

A Siemens S7-300 input card pulled from a 2014 machine, ordered as a spare, arrives in a sealed anti-static bag. The label looks correct. Six months later the diagnostic LEDs flicker in a way the original never did, and the buyer wonders whether the part was a factory reject, a remark, or a copy. Authentication questions are not abstract — they are the difference between a one-hour swap and a week of troubleshooting. As an independent China-based industrial-automation distributor and sourcing desk, we screen every used and refurbished line before it ships; this article describes what that screening covers, what it cannot do, and what the buyer's team should still check.

Why authentication questions show up at all

Three patterns drive most questions about authenticity. First, the long-tail aftermarket: when a component leaves production, the documented channel narrows and the grey market fills the gap. Second, the genuine-but-not-original case: a part that left the factory line but was rejected at quality control, refurbished outside the manufacturer's process, or remarketed with a later date code. Third, outright copies: rebuilt housings carrying original-looking labels, PCBs with the right silkscreen but different component populations, or modules whose firmware identifier does not match what the marking claims. The buyer's question usually arrives in one of three forms. «Как проверить подлинность модуля ПЛК?» — how to check that a PLC module is genuine. «Что делать, если деталь выглядит не совсем как оригинал?» — what to do if a part does not quite look like the original. And «Можно ли отличить восстановленный модуль от подделки до установки в шкаф?» — can a rebuilt module be distinguished from a fake before install.

What an authentication screening covers

Screening is layered. The first layer is the sourcing record: where the line came from, who handled it, and whether the channel matches what the buyer was told. The second layer is the marking on the unit: the part number, the date code, the serial number, the hardware revision suffix, and the certification marks. The third layer is the physical unit itself: the PCB colour and silkscreen, the component population, the housing finish, the connector type, the label adhesive pattern. The fourth layer, where possible, is functional: power-on behaviour, firmware identifier readback, diagnostic LED sequence, and basic I/O sanity. Each layer produces its own conclusion, and the layers are reported separately rather than rolled into a single yes/no verdict.

Sourcing record means the chain is documented. A line drawn from a 2018 machine teardown in a German factory has a different origin profile than a line drawn from an unlabelled pallet at a Shenzhen trading company, and that origin profile is reported on the quote. The buyer's question on authenticity is partly an origin question — «откуда эта деталь?» — and an honest answer starts with where the line came from rather than a generic assurance.

Marking on the unit is what most buyers instinctively reach for, and it remains the most useful single check. The part number is checked against the manufacturer's published format. The date code is checked against what was actually shipping in that period. The hardware revision suffix is checked against the datasheet for that period. The certification marks — CE, UL, CSA, EAC where present — are checked against the markings layout that the manufacturer used at the time. A module whose CE mark sits in a position the manufacturer has not used since 2014 is a marker, not a verdict.

The physical unit check is where training and experience matter. PCB colour, silkscreen font, component population, housing finish, connector type and label adhesive are all features that experienced eyes compare against a known-good reference. None of these differences is conclusive on its own — a manufacturer can change suppliers over the product's lifetime — but several differences together tell a story.

The functional layer is the most informative where it is available and the least often available. A digital input card can be powered on a bench, given a known input, and read back through the diagnostic LEDs or a programming terminal. The firmware identifier, once read, can be compared against what the marking claims. A CPU module such as the 6ES7212-1AE40-0XB0 can be loaded with a test program and observed for unexpected behaviour. Where the line is testable, the test is run and the result is recorded; where the line is not testable without a full machine, the quote says so.

What authentication screening cannot do

Screening reduces risk; it does not amount to a manufacturer's authenticity guarantee. The desk is an independent distributor, not an authorized distributor for any manufacturer in the catalog, and the desk cannot certify a unit on the manufacturer's behalf. The chain of custody cannot always be reconstructed — a part may pass through several intermediaries without paperwork, and a clean physical examination does not always reach the level of certainty a buyer would prefer. Some authentication signals — the firmware readback that proves a CPU is what its marking says, the X-ray that proves a chip is what its part number claims — require equipment and processes that an independent desk does not operate.

The desk can also not certify a unit as factory-new when the unit is not factory-new. A line described as "new surplus" means documented-channel new old stock, not currently in production; the unit may be several years old, may have aged electrolytic capacitors, and may carry factory seals that have been opened and resealed by the channel at some point in its history. A line described as "refurbished" means the unit has been restored, bench-tested and the test result recorded against the unit — it does not mean the unit is the same as one that left the production line yesterday. The vocabulary is exact and the buyer should treat it as exact: condition, test status and warranty are stated per line before commitment, and the only honest description of a used unit is that it was pulled from a working machine, inspected, photographed, and shipped as pulled.

Where the manufacturer does not publish a figure — the firmware revision of a particular production run, the hardware revision of a particular date code, the certification scope of a particular suffix — the axis is reported as not stated by manufacturer rather than filled in from a similar-looking product. The temptation to fill in unknowns from comparable units is strong; the discipline is to leave the unknown axis empty and to let the buyer's engineering process resolve it.

The checks a buyer's engineering team should still run

Even after the desk's screening, a number of checks belong on the buyer's side and they should be planned before the part is installed rather than after a fault appears.

The first is the firmware and hardware revision match. Before installation, the unit's firmware identifier is read and compared against what the engineering record for the machine says is installed. A CPU marked as a particular hardware revision but reporting a different firmware is not automatically wrong — some manufacturers ship firmware updates — but the discrepancy is recorded and the engineering team decides whether it matters for this machine. Where the engineering record is silent on the revision, the install is treated as a deviation and the deviation is logged.

The second is the I/O sanity test. Where the line is a digital or analog module, it is powered on the bench with a known input or output, and the response is observed. A digital input that does not register a known input signal, an analog input that reads off-scale, a relay output that does not switch under command — any of these is enough to put the install on hold and to bring the unit back to the desk.

The third is the documentation check. The buyer's engineering record often specifies a hardware revision, a firmware version, a configuration block, a project file version, or a serial-number range. Where such a record exists, the unit's markings are compared against it before install.

The fourth is the operator-protection check, and this is the one that is rarely done and that often matters most. Where the module sits inside an operator-protection circuit — an emergency stop, a light curtain, a guard interlock, a two-hand control — keeping the original part in place is the right answer in most cases. Even where the replacement is marked as identical, even where the screening has passed, even where the bench test shows expected behaviour, the protection circuit requires its own verification and that verification belongs to the buyer's engineering process, not to the supplier. Substituting in this domain is the wrong answer in most cases; the desk says so when asked and recommends keeping the original design or treating the change as a redesign rather than a replacement.

Any in-house conclusion the buyer's team reaches should be verified against the original manufacturer datasheet and your own qualification process; the desk's screening reduces risk but does not replace that verification. Where the desk's report names an unknown axis — a firmware revision, a certification scope, a hardware revision suffix — the buyer's engineering record is the source that closes the gap.

What the desk publishes and what it does not

For a used or refurbished line, the desk publishes: the condition (used, refurbished, new surplus), the sourcing origin in general terms, the unit-level pre-dispatch photographs, the bench-test result where the unit is testable, and the per-unit warranty where one applies. The desk does not publish an authenticity certificate, a manufacturer's certificate of conformance, or a statement that the unit is "factory original"; those documents belong to the manufacturer and to the manufacturer's franchised channel, and an independent desk that issues them is misrepresenting its position.

The buyer's quote reflects the same boundary. Where the line is screened and passes, the quote describes what was checked and what was found. Where the line is screened and a marker is found, the quote describes the marker and offers the buyer the choice to proceed or to substitute. The Incoterms on the quotation — EXW, FCA, DAP or DDP — are stated per order; payment is by bank transfer against a proforma invoice or via Payoneer, confirmed at order placement rather than promised in advance. Where the line cannot be screened to the level the buyer requires, the quote says so and the line is offered only with the buyer's explicit acceptance of that limit.

For orders that include authentication-sensitive lines, the desk's recommendation is to request the pre-dispatch photographs at quote stage, to read them against the known-good reference before confirming the order, and to plan the in-house checks described above into the install procedure rather than relying on the supplier's screening alone. The two layers — supplier screening and buyer-side verification — are designed to be complementary rather than redundant, and skipping either leaves a gap.

Cases where the screening approach changes

Three cases shift the screening model and the buyer should be aware of each.

The first is a long-tail discontinued line. The part is no longer in production, the manufacturer's documentation is older than the buyer expects, and the available stock is drawn from the channels that accumulated over the product's lifetime. Authentication screening on these lines is harder, not because the desk's process is different but because the markings changed across production runs and the reference set the desk compares against is broader. The buyer should expect the screening to take longer and the report to include more markers; the line should not be installed until the buyer's engineering team has worked through the markers.

The second is a line drawn from a machine teardown. Here the unit is genuinely used, the screening looks for signs of damage, environmental exposure, and modification rather than for signs of forgery. The bench-test result on a teardown unit is reported as pulled, the photographs show the unit's actual state, and the warranty on the line is shorter than for refurbished stock. The buyer should treat a teardown unit as a maintenance spare rather than as a long-life component.

The third is a line where the buyer has a specific revision requirement. Where the engineering record names a particular hardware revision, firmware version, or configuration, the desk searches for that revision rather than for the part number alone; where the revision is found, the markings are documented; where it is not, the desk reports what it found and the buyer decides whether to proceed with a different revision.

A short list of red flags the buyer can check in five minutes

The label. Adhesive pattern, font weight, alignment, the position of the certification marks, the spacing of the part number, the colour of the ink under the barcode. A label that is slightly off — the part number aligned left when it should be centred, a CE mark that sits in an unusual position — is a marker.

The PCB. Colour of the solder mask, silkscreen font, plating finish on the connectors, presence and position of test points. A PCB whose solder mask is a slightly different shade than a known-good reference is a marker.

The firmware identifier. Read with a programming terminal before install, compared against what the engineering record expects, and recorded. A firmware identifier that does not match the marking is not automatically wrong, but the discrepancy is logged.

The diagnostic LEDs on power-up. The expected sequence is in the manufacturer's manual; a sequence that diverges is a marker. The divergence is not always a fault — the manufacturer's own firmware updates sometimes change the sequence — but it is worth knowing.

The connector moulding and the housing finish. A connector that is a slightly different shade, a housing whose surface finish is slightly different from the reference, is a marker. Manufacturers do sometimes change suppliers, so the marker alone is not a verdict; several markers together are a story.

What the buyer should send to the desk when the question comes up

Where the buyer's question is "is this part genuine" and the part is already in hand, the most useful first message is the part number, a clear photograph of the marking including the date code and the serial number, a photograph of the unit in full, and the machine it is destined for. The desk's response is what the desk knows — the sourcing channel, the markings against the manufacturer's format for that period, the comparison against known-good references — and what the desk does not know, which is reported as such.

The honest report from the desk on a passed line is: screened against [list], no markers found, condition [stated], test result [stated]. The honest report on a line with markers is: screened against [list], markers found on [axes], buyer to confirm before install. The honest report on a line that cannot be screened to the buyer's requirement is: this line is outside the screening scope we can offer, offered as-is with the buyer's acceptance.

The closing boundary

Authentication screening is one of the more honest conversations an independent desk can have with a buyer, because the limits of the screening are easier to name than the limits of cross-reference work. The desk screens what it can screen, reports what it can report, names what it cannot, and leaves the install decision to the buyer. The buyer's engineering team then runs its own checks — the firmware readback, the bench test, the documentation match, the operator-protection verification — and the install proceeds with both layers of work behind it.

Where the part is a candidate for an operator-protection circuit, where the engineering record pins the design to a specific part, where the certification scope of the machine would change with a different unit, or where the buyer's quality system requires documents the desk cannot issue — those are the cases where the right answer is to keep sourcing the original or to treat the change as a redesign rather than a replacement. The desk will say so when asked, and the answer is the same whether the question comes from a panel shop in Moscow, a maintenance engineer in Yekaterinburg, or a machine builder in Minsk. Delivery to Russia and CIS destinations is arranged on a per-order basis as stated on the quotation; the desk screens end users and end uses before quoting and declines transactions that cannot be screened.

The next practical step is to send the part number, the marking photographs, and the machine the part is destined for; the desk responds with what its screening covers and where the limits are. For an authentication-sensitive BOM, send your BOM through the procurement page so each line can be quoted with its condition, its screening report, and its pre-dispatch photograph record attached — and you can request a quote per line before committing to any of them.

Data Notes

Catalog evidence (current cycle): 6ES7212-1AE40-0XB0 (Siemens S7-1200 CPU, score 95, 2026-06-29) and 6ES7211-1AE40-0XB0 (Siemens S7-1200 CPU, score 90, 2026-06-29) — both carried in the catalog as examples of current-production Siemens CPUs subject to the same authentication logic described here. Scores, condition language and per-line screening description are reproduced from internal catalog records.
Methodology: Authentication screening as described here is the desk's internal procedure; it is not an industry-wide standard, and other independent distributors may apply different layers or omit some of them.
Disclosed limits: The desk is an independent distributor, not an authorized distributor for Siemens or any other manufacturer in the catalog; the desk does not issue authenticity certificates, certificates of conformance, or statements that a unit is "factory original". Where the manufacturer's original line is required, the buyer should source through the franchised channel.
Operator-protection boundary: Where the candidate part participates in an operator-protection circuit, the substitution rules are different and the determination belongs to the buyer's engineering process rather than to the supplier.
Currency of information: Last updated September 2026. The screening logic is reviewed when the catalog adds a new family or when a manufacturer's PCN changes the markings layout for a currently-shipping series.

By the AoCtrl Sourcing Desk, an independent China-based industrial-automation distributor and sourcing desk serving overseas panel shops, machine OEMs, plant MRO teams and repair shops — including buyers in Russia and the CIS.

FAQ

How do I check if a Siemens PLC module is genuine before I install it?

Read the part number, date code, hardware revision suffix and certification marks against the manufacturer's published format for that production period, then read the firmware identifier with a programming terminal and compare it against the engineering record. A clean match on marking, firmware and connector moulding is a strong signal; several markers off are a reason to put the install on hold.

What is the difference between "refurbished" and "factory original"?

Refurbished means the unit has been restored, bench-tested and the test result recorded against the unit; it is not a unit that left the production line yesterday. Factory original is a description that applies to a unit sourced through the manufacturer's current channel and carrying the manufacturer's current warranty; an independent desk does not issue that description.

Can a counterfeit industrial automation module be detected before installation?

Several markers can — label adhesive pattern, PCB colour, silkscreen font, connector moulding, firmware identifier readback — but no single marker is conclusive and an independent desk's screening reduces rather than eliminates risk. The strongest check is the firmware identifier read against a known-good reference.

Do you provide an authenticity certificate with the order?

No. The desk is an independent distributor and does not issue authenticity certificates; those documents belong to the manufacturer and to the franchised channel. What is provided per line is the condition, the sourcing origin, the pre-dispatch photographs, and the bench-test result where the unit is testable.

What should I send if I already have a part and want it screened?

The part number, clear photographs of the marking including the date code and serial number, a photograph of the unit in full, and the machine the part is destined for. The response covers what the desk can verify from those materials and names the axes it cannot.

Does the pre-dispatch photo record substitute for an authenticity check?

No. The pre-dispatch photo record documents the unit's condition at the moment of dispatch so arrival condition can be compared with shipping condition; it is not a substitute for an authenticity check, which is a separate layer that looks at markings, sourcing channel and, where possible, firmware readback.

What if the engineering record names a specific hardware revision?

The desk searches for that revision rather than the part number alone. Where it is found, the markings are documented against the engineering record; where it is not, the desk reports what it found and the buyer decides whether to proceed with a different revision.