Very exotic coin, rare and valuable despite the impairment. IMO a coin like this should be slabbed for authentication purposes if not for grade. Maybe the seller doesn't believe in slabs, or maybe he realizes it would likely go in a "Genuine" slab at PCGS
or a Details slab at NGC and therefore would be harder to sell for $9,000.
I agree it looks like the "Standard Silver Dollar" Judd 996 but according to Heritage that pattern has a reeded edge. Judd 997 is silver with an identical design but a plain edge so I would assume that is the correct ID for this coin. Heritage sold one graded NGC PR-64 Cameo for $9200 in 2009. The coin you posted is a Cameo but can't compare to the Heritage coin in quality due to the hairlines. IMO the price should be a couple grand less than what the seller is asking.
There were a whole boatload of 1870 patterns struck, in silver, copper, and aluminum, in dollar, half dollar, and quarter dollar denominations, with plain and reeded edges. For a real challenge try assembling a complete year set!