Gearbox numbers on the rib-cases are on the driver's side of the main case. Date codes are on the little ear sticking out the driver's side rear of the main case.
Back in the late 70's and early to mid 80's I used to rebuild about 10 - 20 gearboxes a year for a Charlotte, NC area salvage yard. He would bring me 3-5 a month and I would make as many as I could from the batch. Collected up quite a bit of stuff over the years. These days, I'm building about 6-10 a year. Mostly the straight-cut close ratio or Hewland/Webster conversions. But also do a few stock rebuilds.
With all those gearboxes passing through my shop, I would see stock stuff from all sorts of years, Goldseal replacements, Silverseal replacements and lots of backyard mistakes. The most common error is the oil application. Many came through with gear oil in them. Not something that worked well. These days with the nice synthetic gear oils that are more like motor oils in viscosities, it is not so much of a catastrophic consequence.
Check on the actual gears themselves. 22A is a very common prefix for the internal supporting parts.
I saw 2 Bugeyes in May of 1973 at my girlfriend's older sister's house, one a racer, the other a silver street car. Both belonged to the new husband. Had the same reaction. Had 4 Bugeyes of my own before Labor Day. The rest is history. Just brough home another 1275 engine, a 4.22 diff and a 3.9 diff last night. Quite an addiction as my lovely bride would say.
Mike Miller