[DonVoigt]

I doubt it is a period "field" repair; magazines were expendable and would not have been repaired in the "field". Maybe the base replaced at some low unit level with a new one- but not by two pins and drilling holes in the tube. JMHO.

You really can't restore that magazine, if it works - use it or what ever. An original base is quite expensive, and the tube has been modified already.

If you want a typical , unmodified mag for display - there are plenty for sale.
If you want one for shooting, use that one, or buy a mec-gar new mag or two.

Still a very good deal.