Toss-up between a straight 20 and a details coin. I went with 20 - but what is going on in the obverse fields? Looks really weird.
It initially looked weird to me, too, like a fingerprint, but specialists told me that's a normal characteristic of the variety. I have since seen it on other pieces. This coin actually had very nice surfaces. I briefly had some small pangs of seller's remorse after parting with it. In fact, I would go so far as to suggest that the only reason that odd die characteristic is visible at all is because this coin in fact had far above average surfaces.