Coin and holder must be undamaged. Mintage just 600 some were spent, melted, buried, mutilated, lost, etc. Many tallied in the population reports are resubmissions or crossovers of the same coins. Far too rare and unprofitable to promote, so demand and thus prices stay very low.
Dealers instead heavily market BILLION-mintage modern coins, which generates artificial demand, vastly inflated prices, and GIGANTIC profits. Easily PR67 in the giant scam that is the raw coin (and "third world" slab) business, even without the usual doctoring.
Neither the usual fake brilliance nor phony toning are present. The item "1891 PCGS PR64 Mintage 600 Colors!Final Year Seated Half Dollar PROOF 50C" is in sale since Tuesday, November 10, 2020. This item is in the category "Coins & Paper Money\Coins\ US\Half Dollars\Seated Liberty (1839-91)". The seller is "certifiedcitynet" and is located in Philadelphia, Pennsylvania. This item can be shipped to United States.