Great watch David, I bid a lot of watches, seems like I recently bid on this one. It's a '25 I think, pretty sure there's a circle date stamp near the crown. This is another of the early movements with a period in the serial number. I wonder what that is supposed to signify.
We do have this one ID'd a couple times as Senator but I'm not sure I agree. The engraving on the Senators in the adverts we have is quite different.
This advert is December 1926: 
http://www.mybulova.com/sites/default/files/vintage_ads/1926-Bulova-AD-…
This advert is December 1925 and show a completely different watch: 
http://www.mybulova.com/sites/default/files/vintage_ads/1925-bulova-ad-…
I'm going with the flow as a Senator ID but I will be tentative as well. Either way, this is a wonderful, early Bulova wrist watch in fabulous condition!