I would guess not more then 10K were ever made (all
Altairs including the 680,Attache and Sherwood). If
you (or anyone for that matter) has serial number data
that disagrees with this conclusion please feel free
to correct me!
I don't have serial number data to correct you with, but keep in mind
that MITS was notoriously "odd" with regards to serial numbers. I'm not
sure what internal meaning those numbers ever had.
I read an article that said that the 8800 supposedly sold 10k units in
the first year (I'm not sure how many were delivered, or how many of the
kits were completed versus scrapped or cannibalized for parts). The
8800a and b lines were similarly successful, give or take, with the Bs
being more so because of their higher quality. I don't know jack about
the numbers for 680s, Attache's etc.
10k sounds a bit low, even if 50k might be a bit high.
Erik S. Klein