It gets interesting...the little research I have done revealed LUDLOW only makes the packaging.
The markings seem to refer to the wrapper, not the contents.
I can't speak about the marvellum wrapped mags but suspect the same story.                          Shell development company, I don't believe ever made magazines, but now I have more to research. Why would they patent a GI mag?
See if the witness holes are in the right places, compared to a mag of known origin.
My guess is they are "off" one hole.
Also compare to the cheap $5 "gunshow" mags...I find them the same except for the stamping on the bottom...but even the finishes were the same.
That's all I can speculate so far.       Use as "range mags", there is no harm done.
If I dig anything else up, I'll pass it on .

Ludlow, (ludlowcp.com), in fact, only makes wrappers, including MILPAKII. as seen on that website.
Shell development company is a firm in Emeryville Cal. , with no relation to the huge petroleum corporation.  They don't seem to make any mags there either.

Wherever they originate from, the market is sure flooded with 'em!
I have seen some wrapped, some not...the stamped ones that weren't in wrappers were next to unmarked ones and looked to be identical but the unmarked ones were $1 cheaper.