AU-50 looks spot on to me. Nice coin!
It's a typically soft San Francisco strike for the date. Like most early buffs, the softness is most obvious in the central devices. Part of what you are seeing is a difference in die state (EMDS obverse, LMDS reverse). Another part is the much heavier die polishing on the reverse. Note the deep polishing marks on the buffalo's right rear leg and the buffalo's head, to reduce evidence of the "LIB" of LIBERTY / rear leg clash and the second feather / buffalo's head clash. This is enough to make the reverse look slightly more circulated.