MK bagged Pelts and Peltier bagged MK's. Here are some other Peltier "printed on bags" (as I call them) that have MK's. Union Made - hey, kids of Union fathers will clamor for them (back in the 50's....).
I have several different bags from Montrose like those. Some are made in Japan and, at least one, made in Taiwan. No idea on dates but none have the vertical seam although foreign ones didn't that I am aware of. They could be 60's or 70's.