The Joy Of Hinged- Article On Regumming.

Very suspicious of the gum on that 30 cent. Looking at it I see shadows that seem to indicate that the gum stops shortly before the edges of the perf holes and that match the shape exactly. This is particularly noticeable on the bottom left holes, but is also visible elsewhere. Stamps were gummed and than perforated, so the gum should go right to the hole, but not right to the edge of the tips where separation will remove some of the gum at the edges. Separation will also leave some paper fibers showing (this stamp has a few, but not enough), and the lack of gum at the edges will not look almost exactly the same across a row of perfs. These look filed to me.
Compare the perfs carefully to those of the pair, where the gum goes right up to the holes and also look at the fibers on the perf ends. These two stamps were only issued about 20 years apart, so there should not be this much difference in those two areas.
As I said before, I am far from perfect in this area, but that stamp sends up many red flags to me.

It's legit and came in a collection with a PF certificate.

From What year?

In the right environment, yes. But in a normal, temperate environment, I think it unlikely.

Anecdotally speaking, take a look at the quality of Mint, OG US stamps from the 19th century. Even stamps with seriously compromised gum are generally sound.

Obviously, there are exceptions. Germany's OSTROPA sheet and Hindenburg airmail stamps have H2SO4 in the gum, and will eventually destroy the stamps. But I have yet to see a US stamp irreparably damaged by original gum.

If damage from original gum hasn't happened after a century, it most likely will not any time in the distant future ...

Brian

2001. The name on the Certificate is the owner from which the collection was purchased (Actually from his Widow).