One more "what is it"

In 1979 I went to the local bank and got a roll of the new dollar coins. The roll was as issued BU from the mint. This coin was in that roll. Is it just a grease filled die or something else? I've had it since 1979.
Have a good day, Gary
2
Comments
Post mint damage.
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I think it's a grease fill die error.
Collector
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If all of the coins were BU in the roll, maybe this was a test strike. That is not the proper name for it though. Maybe @ErrorsOnCoins could help.
Adjustment strike? Like when they set up the press and are adjusting the force?
Mr_Spud
Not an adjustment strike. An adjustment strike wouldn't have full reeding. Struck with filled dies will have full reeding. That is what it is, struck with filled dies.
Agreed.
That is quite a coin to be found in a new roll.... Seriously filled dies... Unique for sure. Cheers, RickO