Pardon for what I guess is a really easy question but this amateur couldn't find the answer. What do the numbers for watch stems mean? For instance a 401-906...I'm guessing it refers to the dimensions or function but I couldn't find any information on this. Specifically I need to know what the differences are between a 401-1370 stem and a 401-906 stem. I would like to replace an ETA 805.112 with the better ETA 955.122 movement and I have read that the 955 is a drop in replacement for the 805 and the only major difference I see is the 805 uses the 401-1370 stem and the 955 uses the 401-906 stem. The watch is a WR one with a screw down crown so I assume if there is a difference in length of the stems it will cause a problem. Oh, I should mention...both stems are a tap 10.
Thanks for your help.