The letter would most likely state what the revolver was when it left the factory. Rework/repair records are about impossible to access and of little value to collectors at this time.

44 Magnum caliber would have been an option, uless S&W would not do it because of the frame issue. I doubt if the heat treatment of the frames was different, but most gun manufacturers are quite conservative and don't want to do conversions that "may" cause a problem.

Bill