Recently bought this fun coin. The field looks very flat and regular where the 4th digit should be, but it's probably just a grease-filled die.
In the seller's photo, I could have sworn I saw a second "3". Maybe it's the "Martian canal" syndrome!
... and looking at this Abe live and in person through a color-corrected loupe, there's no sign of ANY number. The possible corner of the possible "7" is nothing but a scratch. One could go nuts squinting at this kind of stuff!