I doubt this coin has a mintmark. The mintmark on Barber quarters and halves is well-protected by the adjacent design elements. It is usually obviously present even when the coin is even more worn than yours.
Of course, if you do have a 1901-S quarter it is well worth having it slabbed, in any condition.
Of course, if you do have a 1901-S quarter it is well worth having it slabbed, in any condition.


















