What it is and what it fits
The Siemens SIRIUS 3RT1935-5AH01 is a 48 V AC magnet coil for Size S2 contactors, terminated with screw terminals. It's the drop-in replacement coil for any SIRIUS S2 frame — if the contactor body is good but the coil is open or shorted, this is the part that goes back in without modifying the panel wiring. Rated coil voltage is 48 V AC at 50 Hz, with an operating range of 0.8 to 1.1 times the rated voltage — so it picks up reliably down to about 38.4 V and holds in up to 52.8 V. That's a standard ±20% tolerance band for industrial contactor coils; anything outside that and you're looking at a weak pull-in or a burned coil.