DC , without the presence of the U.S. marking I would personally
value it at 1/2 of a comparable marked and condition gun.

I don't know where this puts you money wise.
But without the proper markings I would want a factory letter before any money changed hands.

In my brief experience the U.S. property mark is almost as valuable
as the gun itself.

Good luck
Allen

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NRA cert.instructor&R.S.O.