It has been known for some time that the DPRK had numerous stamps designed that were numbered in the Korea Stamp Corporation’s DPRK Stamp Catalogue. Some of these items were illustrated as unissued stamps, but other “others,” until this past year, were not illustrated at all. Why they were not illustrated (though numbered) prior to that is a mystery to me. It would seem to be a simple inference that certain stamps were prepared, for issuance, but were, in fact, “unissued.” In fact, that is the word actually used in that catalogue after those numbers that were given.
Moreover, now that items said to be those stamps have appeared on the market, we assume that the only possible conclusion one may draw is that these stamps were all actually in the prepared stage of production and simply now are being shown for the first time. It is also assumed that these were residing in the vaults of the main post office in Pyongyang. I have no way of knowing that other than word of mouth.