I think this is an interesting discovery of Blue Note Reissue Series by King Record.
You know, recently I got some Blue Note Reissue pressings by King Reord, GXK Series with OBI. And...amazingly, all of these copies have nothing but PERFECT SLEEVES, the condition is just NM with no stain.
I already talked about the sleeve condition of Japanese pressings. Many of them have distinct noticeable stains especially King Record reissues. The reason why sleeves got a lot of stain is because our humid climate attracts molds. The molds are the main cause of those dirty stains on the sleeves. Remember?
The copies with immaculate sleeves I obtained are from a place called Hokkaido. Hokkaido is the most northern part (a big island) in Japan. All through the year, the climate in Hokkaido is not like in main island. It is cool and not humid. So I believe, most of the record sleeves stored in Hokkaido were ont affected by those molds causing stains.
Anyway, that is my assumption and to me, it is an interesting new discvery, haha!