This is an interesting anomaly perhaps relates to the hubbing process and strangely seen mostly on coins from the Denver Mint. It’s also perhaps one of the hardest errors/varieties to photograph! You can see dimpling inward from the lettering around the rims. https://www.error-ref.com/design_extention_dimples/ Has anyone here ever found one of these?
Very interesting, never heard of it. My initial question after reading the link is - how do they know it's on the die? It seems to me that it's metal flow, so was it during the strike and coin specific, or during the hubbing process and die specific, or is it the strike and common because of the design?
It's a good question. I think the initial idea that it was on the die was that, when it was discovered, it was found on three Andrew Jackson dollars from the same die. Now that more have been found, I suppose it's possible that it is strike related rather than die related. I'm not sure anyone actually knows what causes it anymore.
I was wracking my brain for where I'd seem something similar before. Could it be the same process that creates trail dies and so-called wavy steps? (Both caused by the same thing) To me those share a lot of similarities with the design extension dimples. If so it's on the die and a strange result of die polishing. https://www.error-ref.com/trails/ and a whole site devoted to them http://www.traildies.com/
