I dont think the numbers will have been in a different place...
I have attached a photo of a SIII gearbox (awaiting stripping down..ie, I dont have the funds for a set of new bearings at the moment!
) the arrowed bit is the box number. The red line is where I have also seen the number stamped. Sometimes too, you might get a factory reconned gearbox..that will have a brass plate on the bellhousing with the number stamped into it, and the date of reconn.
Hope that helps! Sorry the pic is a bit out of focus...my camera is not very well...something else awaiting replacement!