it's a business strike, but I already know what you mean, what makes you think it's a proof, it's a solid strike with a squared rim.
My "opinions" and people will disagree....
I've found coins like this from various years roll hunting, my first guess is, came from a mint set and released to the wild.
or guess #2, it was struck in San Francisco or West Point to help out with production, not a proof strike, but not done at Philly on the rapid machines production presses.