Guatemala Stamp From 1875 Sc#8

I wanted to show you this Guatemalan stamp from the 1875 issue, SC#8. It's one of the few classic stamps I own in MNH condition, and although it has a small foxing spot on the left 2, it looks very nice and fresh. I think it's original, but any observations are welcome. What surprised me is that I classified it some time ago using a standard 2017 Scott catalog, but I recently saw it in a specialized 2020 Scott catalog with a very noticeable increase in value… now I'm curious to see how its value has changed up to 2026…

Shouldn't that stamp be green? This looks like it is slate.

Also,have you checked it with a uv lamp?

There is a very strange bright white area around the eye or a discouloured area around it. There is a curvy blackish grey smudge to the right of the first "A" in the right margin. If it is genuine and an 1875 stamp, it might have been cleaned and re-gummed.

I'll upload better pictures...the color is a very nice green, the rubber isn't visible...and I haven't even UV tested it yet. I've compared it to similar counterfeit examples and it seems too "perfect" to be a fake...




The stain next to the first A on the margin, under a microscope, appears to be ink displaced from the stamp itself; I think this because of its green color.