Interesting cuts for sure. I have a No1 MkIII* Ishy that was "reworked" by Golden State Arms back when you could order guns through the mail.
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Most of the adulteration to this rifle occured before I owned it. But, since the original rear sight had been removed and the replacement left much to be desired, I put the XS scope mount on it. Before I did though, it had several cuts that looked just like the ones you have pictured.
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Here is a closeup of the surviving cut. Wherever that rifle came from I'm sure it has had adventures. Imagine the stories it could tell.