I had a similar problem when local law enforcement stole my pistol. I registered my Single Six Light Weight alloy cylinder, no rings or chips in the finish, per regulations. 2 days later I received a call from the department to bring all firearms and paperwork to the station, no explanation. So ok, I did nothing wrong maybe because of the number registered or question of one of the description. Showed up he needed to see three of them, a Sharps 50-70, top break Smith and Wesson, and the Single Six. He told me they were stolen and he needed to confiscate them. He showed me the report that came from his data base for the Ruger. It read, doing this from memory of 18 months ago, Make: Ruger Cal: 22 Model: std SN: (same number) Date: it was early 70s Reporting department: Toronto. I think that was it, but you get the picture. Ok too easy, translated all for him, why it is not mine, but he needed to get the police report. Understood, support law enforcement and let do their job. 2 weeks later no report yet. Long story short I contacted all police departments and received the reports faster than him. Contacted Ruger records department who was able to give me information that my Single Six was shipped in the states and a Standard Model was shipped to Canada. Also showed him that prior to 1968 manufactures could repeat serial numbers on different models. And some other minor evidence to support me like pretty pictures from the 60s showing both guns. His response… A gun can be converted without changing the serial number. To clarify I asked, a alloy revolver can converted into a steel auto loader without altering anything around the serial number. Answer is Yes. I really wanted to meet the gunsmith who can do this; still hasn’t given me their name.
Had to get a hold of his highers up to the Provost Marshal and get a JAG attorney involved. Luckly it never went to Canada and I did get the pistol back a couple of months later but it now has a ring on the cylinder and a snazzy evidence box with its information on it.