identifying 4 speed automatic

is there a place to find out details of what type of transmission I have purchased and where it originally lived? I bought a 4 speed automatic from anther member and I have been trying to find out the exact type of transmission (I think it is a 42RH) and where it came from (year, vehicle and behind what motor), but I have yet to find a site or source that can decode the number on the pan rail pad which is:

PK4 505465 0295 7958

Thanks for any assistance!!!