I bought this item a few months ago, and got a good price because it was a bit of a wreck. The paper is listed in the catalog as "pelure" (debatable) which is very thin, so marks and remnants from hinging tend to be visible right through the paper. They look like thins, and can bleed through to the surface creating what is called a "translucency" or "gum soak."

But... a few minutes in a water bath and a couple of days between blotters in a press, and ...

a $200 item becomes much more (despite the catalog)
One has to be careful handling thin items like this while they are wet, for they can easily tear or get pierced by the tongs. But once you get the hang of it, you can safely lay these out on a blotter and press them completely flat so that they dry without a ripple.
Some things are worth the effort. Unfortunately this won't work for stamps where you want to preserve the gum - which should be obvious. But aesthetically I tend to prefer a clean unused no gum over o.g. with paper translucencies.
[I have a couple more on India paper that are drying right now. I'll let you see how they turn out later.]