Definitely looks like the concentric circle over stamp for non-military usage. As the note states, could be prison guards, police or school usage. I have two of these rifles. The first is complete and has a full, unmolested mum. The second is incomplete, missing the stock and associated metal. This one has ground smooth mum and inscription and new inscription stating "for blanks only" stamped along with the bore being drilled out smooth. I've been trying to find a stock for years with no luck.
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