The Siemens 3RT5975-5AV31 is a SIRIUS-branded magnet coil designed specifically for size S12 contactors, used with 3-pole contactors of size S00. It's the replaceable coil assembly — the part that pulls the contactor in and holds it closed — not the full contactor itself. If you're swapping a failed coil on a S12 frame and the nameplate says 420 V AC/DC, this is the drop-in.
The control supply voltage type is AC/DC, meaning one coil covers both worlds. That simplifies spares: one part number for a 420 V line, whether it's a VFD DC bus or an AC control transformer.