John1 called it, it's the doubled master die. It covers all three mints and you will see more, than not, when you are looking at a 72. Here is a link to check out, scroll all the way to the bottom, the very last listing, it's listed as 1972 1¢ WMDO-001. Yours is smoothed over and beat up a bit but you can see it really well on the "N", of IN, on yours.
LINK
https://doubleddie.com/384301.html
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