Always nice to find a small date 91.
Are any of those marks on the obverse severe enough to have dented the coin ? The neck-ear-ribbon triangle would be the area corresponding to the wear on the reverse. If dented, the other side would stick out a bit and wear faster.
If it's not dented, then it would appear to be like many 1900 and 1901 cents that were minted with a concave obverse and convex reverse. ( I just got dizzy writing those last five words

)