Movement symbols are year manufactured for the movement only. No way to really know when the watch hit the streets except for the ads. Therefore, without an ad there is no other way to accurately date the case.
I'm still confused if the movement serial number indicates 1926 with a square date symbol.
A patent date on this case is irrelevant, it doesn't have a hinged case. The PAT.JUN.10.1924 was for the hinged case with movement cover.
Model Number 3155 is the earlyist date for a Banker states 17 jewels. In 1925 the model numbers were changed to names. The jewling differences in the 1925-1926 ads & actual 1925-1926 watches are a problem. I have two watches in conflict in the database.
The only reason for my initial comment above was to point out the square movement symbol =1927 the presentation date of 1926 is a definite conflict.
I did misread the jeweling in the 1928 Treasurer ad.