Let me get back to you. I remember that all or almost all of the "real" ones seemed to have one of two contractor's names on them, may as well wait until I can check my hoard.
I bought a dozen from somebody on eBay who advertised them as "real US GI" or somesuch, and they did prove to be the genuine article. Since then I bought a few more at a surplus store where they were out in a can and you could handle them.
A few of the knockoffs I've seen were actually larger... IFIRC, at least 20 percent larger than the real thing. Seems like that might be a good thing- more leverage- but they bent. That was a long time ago, though, so they may no longer be on the market.
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