I have had this Model 80 since 1972, when the Coast Guard advised me to be armed on the way down the Intracoastal Waterway between Savannah and Brunswick, GA, where they said piracy was a problem. I've carried it on more trips down there, but haven't had to do more than brandish it in sight of approaching apparent bad guys, and I've fired not more than 30 Super Vel police JHP rounds over the years, so it's very clean and unfouled. What I would like to find out is what is the meaning of the "625" stamped on the underside of the heel of the barrel. Is it a kind of "sub-model," or something like that? Any info would be very appreciated!