Sweden Mint Stamps With No Gum

Good day all:
A recent purchase has many pages of what are with out any doubt mint stamps. Nothing in high catalog values, all in the 1960s to 2001, but none of them have gum. These were not mis-classified by the seller as they are just in a larger lot of many albums. The question is - as sooo many of these have no gum but are otherwise VF-EX, did Sweden produce stamps for the collector market without gum? The only other scenario I can come up with is the previous collector bought a large collection, could be close to 1,000, of mint Swedish stamps that were stuck to the pages and had to soak them all off. There are used and some with gum intermingled as well.
Your thoughts please.
Thanks
Paul

Some collectors resident in humid climates have removed gum to prevent damage to the stamps.

I'm not aware of any modern stamps of Sweden been produced for collector's market without gum. I think some official reprints of classic Swedish stamps were produced for stamp handbooks or similar, which may be without gum but except that I am not aware of anything else.

Good thoughts and comments. Thanks for the feedback.

Are you sure that some of these stamps were not produced with PVA gum?

PVA gum is matte/dull and appears invisible.

Well I just did a search on PVA gum here and found the following from a post in 2009. Looks like a bunch of my Swedish stamps are in fact mint.

"In the last 30 years, Swedish stamps
have a gum that is nearly impossible to see.
Most other countries are either using self
adhesives or old fashion water activated clear
gum which you can see and feel."

That is the first I've known about PVA.
Thanks all for the feedback.