Rare But Worn 1771 8 Reales Lima Hiapsn Advice And Opinions Wanted

NGC shows Hiapsn as an error valued at X3 or X6 times the value of a non-error piece.
But at such a poor level of preservation, I'd yield to the experts on this one.
I found a better one sold for $1,100.00

Although not in my KM ... Albert above has verified it as a legitimate error. Assuming real here and I have mentioned several times here silver in its most oxidized state is black. Sedwick can probably confirm that there are many sea salvaged pieces that have turned black. With time the more oxidized metal leaves the coin in this case copper so the surface readings of these silver seawater pieces with time and with slow seawater corrosion actually approach 99% silver as the copper leaches out totally and leaves the alloy being almost pure silver. I have verified several Calzador shipwreck pieces with 99% Ag XRF surface readings. The black is oxidized silver oxide (Ag2O). The lower weight on these sea salvage pieces never makes you think you may have a 99% silver alloy pieces in your hand as with this specimen although this may be more like 95-96% Ag alloy with some Cu left as a guess since its pretty much INTACT IMO. IT IS A STRANGE PHENOMENON. What is even stranger as I have seen studies of Ag/Cu alloys in this environment is copper migrates to the surface and silver migrates to the core ... so with time there is no more copper left in the alloy per se say >1%. There is nothing wrong in thinking the black could be copper oxide but its not in this case.

JPL

Thanks guys for your explanations and opinions!
Although very corroded I have been able to compare details with pictures of the same issue that I found on the web. For example the slightly lower A in HIASPN, small ridges under the S of the same, the 3 fleur de lis rotated to the right by a few degrees, the 8 not fully closed... But then again I guess a good forger would notice these as well. I agree with Lucky Cuss in that the coin has character.
Unfortunately, not much detail left on the edge.
I found this coin in Lima at a coin dealer's. His asking price was way more then I was willing to pay for it, so I left it. Still happy to have come across it and to have taken pictures for future reference.

Here is the example of the coin from my collection, I think the original poster's coin is probably legit but heavily damaged from either sea salvage or even land burial in a wet environment. I have seen many coins salvaged from off Florida with the top layer of the coin black and flaking off leaving the underlying coin with very subdued features/details and the two tone look of this coin.

Lucky Cuss. Indeed I have come across many fakes here in Peru, like I have posted several in previous threads. The current owner claims the coin was found in a river near Lima. Must have been a polluted river to have affected the coin in such a way.
Jfransch: thanks for posting pics. Hope to own one in at least that condition someday.
On a little side note, not entirely on topic, guess what airline I flew from Lima back to Madrid?

Hi, the coin is autentic, appeared with a couple of 4 or 5 HIAPSN 8 Reales, the provenance was a shipwreck in Lima, the coins were salvaged for divers and sell to the coin dealers in Lima, I talked that year with various dealers and saw almost all the coins.
Regards.