Bought some catalogues, here are some highlights...
Speedmaster 125 still on sale in 1975...
Seamaster de Ville before it was written on the dial...
Speedmaster 2998 for 420 Swiss franks bracelet included...

 

Apparently it says that every Speedmaster 125 is numbered, if my German is correct.

 

Very nice and interesting - thanks for sharing. Those prices make me a bit misty eyed!

 

Never seen the Speedy 125 before. Good looking watch

 

Jedes Modell ist numeriert und daher besonders fur Sammler von Interesse.

Each model is numbered and therefore especially interesting for collectors. [per Google translate]

Haven't heard of this in reality. @Andy K is the man on this. He has a thread trying to calculate/estimate the number of these 125's (and other 1040 movement watches)
https://omegaforums.net/threads/176...-the-speedmaster-125-conspiracy-theory.38904/

 

I would have to venture a guess that the 125 is the Speedmaster that has gained the least value over time, compared to where it started in price, and what they can be obtained for now.

 

I just added the pic in the thread.

 

There was an alphanumeric code on the back of the earlier Speedmaster 125s. At some point they stopped doing this it seems. And per archive extracts I've seen, they were still being manufactured well into 1976:

More charts and such here: http://www.calibre1040.com/cal-1040-collectors-guide-case-references/125-2/