T-10 research input requested

[hubleyman]

I don't have one with a VIN but here's a T-10 I have sitting around that came out of my old April built '63 Corvette. This one has the small front bearing/retainer and is a T10D-1 main case.

I do have a couple of questions though:

1. Why would some gearboxes get stamped with the VIN and some not?

This particular trany has the number 56 stamped in the top just above and near the side cover. Any idea what that number might represent?

I'll also post a couple other photos of the casting date and the previously mentioned number 56....