The Siemens 3RT1936-6E is a replacement contact kit for the Size S2 contactor frame. It supplies four normally-open main contacts rated 60 A in AC-1 duty (resistive load), delivered as four movable and eight fixed contacts with the necessary mounting hardware. This is a service part for maintaining an existing S2 contactor in the field — you are rebuilding the power pole, not replacing the whole device.
The manufacturer lists this part as a phased-out product. The official successor is the SIRIUS 3RT2 series.