I would guess au55-58 range. Almost no wear visible. Coins that close to UNC are hard to grade from pics alone. Nice coin tho! Really neat to find one in the wild like that. Too bad it's not a D or S - it'd be a $200+ coin.
Wow, that's a stunning early date buffalo to find in circulation. Looks like full horn with great detail. I'd guess as others have said around AU - to near UNC condition. Obviously came out of someone's collection fairly recently. Great find!
Btw, since the value of that coin can vary a lot depending on the exact grade, that coin would be worth taking to your LCS sometime to try and get an expert opinion on the precise grade.