Your question is a bit vague but I am guessing your asking how many revisions were made to the Model 15?
Im not sure of the revision number of the current Model 15 offered by S&W , But..
(you can view it on their website and it has a shrouded ejector rod like the model 19)....
You should know that while major revisions merited a change in model dash numbers small things like dropping the diamond in the grip or changing the way the front site was mounted or the hammer spurs shape did not.
Also quite a few changes occurred from its inception when it was a 5 screw gun (1949 1950?) known as the Combat Masterpiece , this was several years prior to the advent of model designations in 1957, One Major change had already occurred as it was already a 4 screw gun by then .