No need for the poll,not an error on the front of the bill that's just the remainder of a tellers stamp from the stack.The bill is just slightly miscut which is a very common occurrence and you still have $20.
People often mistake a teller's stamp mark as an error on notes. When the "stack" has been counted and verified, the teller places a paper band around the notes and then imprints their teller stamp to verify it was counted correctly. Happens a lot as the tellers could care less if the note is now "damaged," as far as collectors are concerned. Just know that it is extremely rare for an engraving error on our currency. Errors like solvent smear, folds (gutter folds), missing or weak inking, possibly mismatched serial numbers, but almost never an engraving error. Keep on looking and good luck. BTW, could you please post Full Image photos next time?
When in doubt send it to me. I'll spend it and send you the change K. It's a spender, thanks for sharing.