I was looking for Plum Blossom stamps on cover on eBay for an article that is being written for the American Philatelic Society’s magazine, when I noticed one of the blue 6 ch in a short set that did not look quite right. This 6 ch was light blue, and casually looking at the image, it seemed to have more perforations than the normal perforations 10 or 11 of that issue. I thought I would take a chance and after bidding on it, and winning this set, I examined it closely when it arrived in the post. Sure enough, it was light blue printed on thin chalky paper and perforation of 12. (See Image 1).

But there was another mystery associated with this stamp. On the reverse side, (See Image 2), there are two Asian marks (Korean or Japanese?). Sometimes on the reverse of stamps, they are marked by the previous owners as fake, as specimens, or as genuine varieties of stamps. Does anyone know the meaning of these marks on the reverse of this stamp? If this stamp is fake, it is outstanding one, as the stamp is not perfectly centered, it is printed on thin chalky paper, like the original reprints and the printing is excellent.

If you have the answer to this question, please leave a comment below.
This is a frame and mirrorwise “6 Chon” in chinese characters. So this is from a preprinted presentation book and the stamp probably the japanese re-print in “chalky-blue”.
Thanks Florian, that is what I was hoping it was. Robert
To make it easier to copy-paste the characters in for instance a search engine, they are 六 (=number 6) and 錢 (jeon/chon, jeon as in 100 jeon = 1 won) respectively.