USMC Lyman 20 power scope
Hello:
I think I have what you are speaking of. It belonged to my father. He worked for the federal Govt., and if I remember correctly , got it on a military base. His duties included visiting numerous bases up and down the Atlantic coast. Again trying to remember, I think he was able to get it on some sort of lease. They couldn't sell it to him, but could grant a long lease : 25, 50, 75 years , I'm not sure of the number of years. When the lease was up, because it was so long, it would be declared scrap, or an appropriate military designation.
This one is like yours-- Lyman USMC 20 power, in a nice maple, or pine dovetailed box. Box also marked USMC. has metal tag with Lyman sights metallic and telescopic on it. Included is an "owners manual" ( cost 10 cents in 1953 ) and a typed parts list dated 1958. My father died young, in 1971. I suspect he acquired it in the late 1960's. This one has never been mounted. After his death everything sat untouched several years. It has accumulated several light rust spots, due to the humidity in Georgia.
Probably more information than you wanted, but you now have some dates to help you.