Although the bridge shapes are different, this is based on the FHF Robert ebauche.
I don't know if this helps but I have an older case filled with stems(Bulove genuine standardized stems)and on the cover there's a interchangeabilty guide.One line lists the 9AN as being interchangeable with:9AT-10A-10AA-10AB-10AE-10AEcs-10AM-10AN-10ANcs-10AR-10AX-10AXcs movements.I don't have a 9AN stem or else I would offer it to you for free.Also I don't know if the stems listed are all interchangeable.Hope this helps.
1924 10AA 16J Asterisk below SWISS to left of crown and 110632 SN
Anyone know compatible Stems for this model, The keyless work has a different yoke and set lever than 10 AE's and 10AN's. HELP!!!
The above 10AA has no date symbol, and is housed in a case with a tentative production date. It also has a movement serial number. The watch record has been dated based on first digit of case serial number, but we see many, if not most of these 1919-1923 cases having serial numbers beginning with a 1. This date/period is partially backed up by a couple tentative ads for the 155 model (I think 1922 ads). Based on the movement signature of Bulova Watch Co. this movement is, in my opinion, 1923 at the earliest- more likely 1924.