I had a thought on the .45 Cal, since I' ve never heard of a .45 c-n-b revolver, but like Redhawk I' m not an expert on what Colt produced and when, but is it possible you are getting the .45 from the ball size. When shooting a C-n-B revolver you normally use a larger ball than the actual caliber. For example in my .44 I shoot both a .451 and a .454. When the ball is seated a thin ring of lead is shaved off the ball, this make a very tight seal between the ball and clyinder, and keeps the ball seated through the recoil when other clyinders are fired.

I don' t know about the year.