Hi Ed
You missed one of the best parts !! What you did not mention and maybe did not realize that 321 is marked ADJUSTED to TWO positions... which was specific to the late 50 and early 60s Seamaster chronographs .... The Speedys at the time where marked unadjusted in comparison...
GREAT WATCH , I wish I had one like that !
Good Hunting
BIll Sohne