The thread was dated 2010 just like your picture. If someone does make a repro with the hold open notch, my google-fu isn't up to the task of finding it. If anyone knows of one being made please let me know.

As long as I'm asking ignorant questions, here's another. Might using a 1915 mag in a 1907 or 1917 have the potential to damage the hold open features on the mag (and NO I don't intend to try)? Has anybody seen this done? Given what I found when purchasing this 1917 it makes me wonder if or how long it might have been fired that way. I don't see excessive wear or obvious damage on this one. As I previously stated the mag is in really good shape.