I respectfully disagree. There was a small production run of those magazines indicated by the mold numbers, and I've also seen them with no mold numbers or stigma. The later is what I would consider pre-production, experimental or prototype. I may have a photo of one with no markings. If I do, I'll post it. I've also heard that they initially used small quantities of Russian magazines prior to RPK-74 production being assigned to Molot.
Under your methodology, at what mold number does a magazine become a production magazine or does it vary? The magazine developmental process is consistent/constant from everything I have read. I don't think there are exceptions to the progression in development. I could be wrong but it would seem very odd to me for mags with mold numbers to be considered pre-production.
Added Info: Just dug out my copy of the rare Russian book "Kalashnikov" (only 1500 copies produced). On page 153 in the magazine section, there is a Izhmash 45 round pre-production magazine with historical description and technical specifications. The depicted magazine has no markings. This book is very scarce and sells for a premium, when you can find one. Last time I looked, I saw one for $1200. Mine is signed by M.T. Kalashnikov himself, which makes it worth that much more.
