Tony;Majic is right about the gun's frame NOT being in the 1928-43 range for the Bankers Special. The Bankers Special was a snub nose(2") Colt built on the shorter Police Positive Frame,as oppossed to the much more famous Detective Special,that was built on the longer Police Positive Special Frame. The longer frame was to fit a longer cylinder to take the longer .38 Special rounds,as oppossed to the shorter(and slightly fatter).38 S&W for the Police Positive and Bankers Special.
Some Bankers Specials were built in .22,and had rounded butts; the .38s are found with both square and round butts. I suspect,that the hard rubber grips yours has,are typical of the earlier production date, as Majic mentioned-and these older guns have a slightly thinner grip frame,fron to back strap,so finding correct wood grips might be difficult.
On a more positive note,I believe your gun was owned by the Stamford (Connecticut)Police Dept. It is just possible that they rebarreled a Police Positive,with a longer original barrel,to get a snub for the detectives,by buying a Banker's Special bbl. from Colt;way to save some $$ in the depression 30's!
Is the front sight a total half moon shape,or is it a slopped ramp on the backside? Colt made some barrels in 1946-47,for Bankers Special, and other models of pre war revolvers,as replacements,that had this newer ramp sight.
Many of these were sold by parts jobbers in the 50's,and guns were rebarrelled-BUT-the gun,in my opinion,should NOT have been sold to you as a genuine Bankers Special.
Bud