Please help identify these 10xx magazines

[Cool Manchu]

That was my initial assumption as well, squidsix, until I noticed they had only 7 witness holes marked 2 through 8. I then made a real close inspection and there are no signs of the mag bodies being modified or sectioned.

I have been thinking about these.
Is it possible that someone had a 4013 and could find 1006 mags but not 4013 mags? They the modified the standard 10mm mags to work in the 4013?
Its backwards from the way we usually do things, but I do backwards stuff all the time.