A Peru 8 Rs 1840 - Mint Error Or Ship-Wreck?

SG=10.238 (~85% Ag), 26.23 grams.

I think those numbers are good enough to pronounce it genuine, too. But the condition is puzzling. The obverse looks to have had something unusual inflicted upon it, while the reverse appears just very worn, but only in the central area (could it have been that poor a strike?). I can see why you posted it for opinions.

I think corrosion in seawater (ship wreck effect) can be ruled out rather easily. The effect is not uniform at all and the edges look nearly MS. For example, there are visual effects on the tops of the letters on the obverse but nothing on the immediately adjacent field area or the area inside some letters. That is not how corrosion takes place in an ocean environment.

The appearance of the surface could indicate a very rough rolling of the silver strip from which the blanks were punched. The features on the figure of standing Liberty that are being discussed are also seen in the field of the coin where they seem to be more subdued as if they were partially obliterated by the force of the strike. This would place this kind of feature in the same class as an adjustment mark. A feature that was on the planchet prior to the strike that simply survived the strike.

The characteristics of a weak strike also show in the lettering - poor infill of the die and a completely missing center of the shield. So it is my conclusion that the dimples have nothing to do with corrosion after the strike at all. The weak strike preserved the original planchet surface.

The SG is close enough that an analytical scale would be needed for greater accuracy. Add to this the fact that Peru was noted for inaccurate assay silver and I would not be bothered.

So I would say the coin looks genuine but establishing an accurate grade for such a horrendous strike is going to be tough.