Series IIA gearbox
This is a late suffix (suffix F I think) main gearbox.
I used this gearbox for a couple of years before upgrading and it works fine. Ist gear is (and always was) a little noisy but apart from that there's no signs of any problems. Note that these gearboxes have no synchromesh on 1st or 2nd.)
It's in my garage in Chevy Chase, MD and I prefer if you come and get it (although I could ship for a few hundred extra.)