I am afraid I must agree with other opinions. The coin has uneven/corroded surfaces and it seems to have been cleaned from the pictures. Condition is EF, corroded, cleaned.
Yes, '21's (and '23's as well) are difficult to find with decent surfaces.
As an example, these are the ones in my collections. Condition is only 'so-so', and the better one has lightly rough surfaces as well, and a planchet defect or pit on the obverse. Paid less than you did, though.
Up to F12 or so '21's are relatively easy to find, in my opinion.
In better grades. however, they become very difficult.