Mike,
In my case, I've never worried one way or the other what any of the 46 or 47 TC frames I've owned were first registered as in my 41 years of shooting them. Never knocked on wood, just never worried about it at all. Not once did anybody question it, probably because I never felt guilty about it so never had a guilty look. For many years when I had the gun shop most of my customers and a lot of the people I shot competiton with were cops. If one had asked, I would have told them I didn't know, I didn't care and neither should they as long as its in an otherwise legal configuration. Bet I wouldn't have been padded for it.
You have to do what you have to do and make your own decision pard, but you now know what I'd do - just forget about it and enjoy the frame.
L.