Do you think this might have been a plainchant error before SSCA Polished the heck out of it for the United States Minted Coin Set 20th century Silver Half Dollar Collection
Might have been, or it might have been a hit. Unfortunately the place you would look at on the back for evidence of a dent is right where the glare from the light is. Now that could be a coincidence, or it could have been done deliberately to hide the bulge, or a bulge could have cause the light to glare at that point.
there may be a bump on the back there or maybe thats the way it is supposed to be kinda hard to tell with the wear and polishing. Maybe it was PMD and it just looks dif from the polishing I do not know it is in a 3 coin set thats sealed pretty well. I know they are just junk silver but I would rather my grandson crack it someday than me.