I once read that the mint had a lot of trouble with the strike on these early nickels. One, the new nickel alloy was harder than the typical gold, silver or copper alloys and two, the rays on the reverse and the size of the shield on the obverse tended to fight each other while these were struck. The rays were subsequently removed for this reason and the striking issues were greatly reduced but not completely eliminated, even with later nickels, until mid-20th century.
Definitely an AU coin, 55 seems good to me.