It doesn't appear to have much luster.
Maybe a little between the lettering.
I'd tend to think that it has been harshly cleaned.
Also, the brown spot, on the reverse, looks like dip residue.
I believe it's spent some time in the Tarn-X tub.
The 1904-S is usually found with weak details, so your coin probaby didn't circulate, even though the high points are flat.
I can't be sure, without seeing it in hand.
You have a key date coin, that appears to have surface problems.
Still, a cool coin to have.
"Aren't you suppossed to be out driving a truck or something jody?"amrad78