Yowza!
There are four elements to a superb
Buffalo nickel:

Matching die states with an early die state obverse and reverse. Check.

Strong strike. Half check.

Minimal clashing and resulting die polishing. Check.

High grade. Check
The obverse is EDS, and the reverse is EMDS.
For a 1917-S, the strike is better than average. Note the complete rachis and calamus on the second feather and the strong date and complete ribbons. Note the exceptional detail on the first feather, reflecting the stronger peripheral strike. On the reverse, note the strong peripheral lettering, complete separation of "F" of FIVE and "S" of CENTS from the rim, the solid mint mark, and clarity of the ground. The central devices are a bit weaker. For a 1917-S, wow.
There is minimal evidence of die clashing, with some clashing evident in EPU and above the buffalo's head (the second feather clash). Very little die polishing has occurred, mainly at the tip of the second feather and top of the buffalo's head.
In terms of technical grade, on the obverse, there is clear separation of the hair from the cheek and forehead, solid detail at the eye, nose, and chin, and deep separation of the hair strands above the knot. The wear on the knot, ribbon, hair, and feathers is consistent with AU-55. On the reverse, the eye, beard, and neck are strong. There is over 75% of the hair on the upper back, and about half on the buffalo's head, the latter slightly affected by the clash polishing. The sinews on the rear legs are visible, and the tail is split, though not bold. There is modest wear on the horn and flank. The reverse would also snag AU-55. The blended grade would naturally be AU-55.
There are a few noticeable contact marks, especially the SW-NE gash on the buffalo's side. These are grade-appropriate.
TPGs do not generally adjust upward for matching die state and lack of clash polishing, but they should. The strike is above average for 1917-S, but not enough to entice a
TPG to bump the grade. The resulting
TPG grade would be a straight AU-55. I wonder whether CAC might see AU-55 as an undergrade?
All in all, a really nice 1917-S. This is a "buy it now" moment, if the price isn't out of line. It's a great coin.