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Interesting magazines.
Too bad you don't have a regular 10mm mag to compare it to.
Is the front face of the mags stamped with MS1 or ES1? Can't tell.
1006 magazines have the mag catches on each sides, same for the 4013 magazines, while 45ACP magazines only have it on one.
1006 magazines have the lock-out nub/bump centered in the middle of the side (front to back) while a 4013 magazine has it more towards the front edge of the magazine, 45ACP magazines have none.
And 4013 have the crimp/welds on the rear edge of the magazine's body to hold the spacer in.
Your magazines look nothing like 4013 for the above reasons.
Your lock-out nub/bumps are centered on the side so that's like on a 10mm, except someone removed them (maybe so they could work in a 4013/1013 as you already suggested).
4013 & 4516 finger rest base plates "look" the same from the side but they're not. (see side view pic below)
Those finger rest bases in your pic #3 & #4 "appear" to be 4516's from what I can see because the thickness between the bottom of the mag body & the bottom of the finger rest base is thinner on 4516 mags. It's almost twice as thick on 4013 finger rest base plates. (see edge view pic below with arrows)
Both 4013 & 4516 are numbered with 2-8 holes.
Your side views are only of the right sides (180 degrees opposite).
Does the left sides have AccuGuide stamped on them?
How many turns in your magazine springs? Kinda looks like (11)?
1006 magazine spring have (12) turns, 4506 magazine springs have (13), while my original (green tint?) 4013 magazine spring
has (11) turns.
4013 magazines (metal part of the body) measure ~4.20" tall on the rear/back edge while the 1006 magazines measure ~4.80".
What do yours measure?
Sure seems like they could have been prototype magazines for a factory 1013 test pistol.
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