It is hard to get by the blob of a mm. It seems that all 79's look like this. That notching ( bottom left)is definitely the identifier. Cherry pickers guide I believe has them at 10$ unc. I probably have three rolls of these (various grades) they are quite common.
It is actually a die chip. The later die states, look like the wing on a mercury dime. Dubbed a winged D.
Looks like a horizontal s in your avatar. I first saw it I was like wow. looked closer and saw what it was.
