It looks like a Unertl (not sure of spelling) that I had in the early 70's. It was one of the best scopes around at that time.
Here's a pic of one of the 1903A1 Scoped National Match rifles used by the Marines as a sniper rifle, scope is a Unertl 8X (USMC didn't use the O3-A4 in WWII).
Scopes of this design, with micrometer click external adjustment, were once favored by long range shooters. The Marine Corps utilized this style of externally-adjusting scope on sniper rifles during WWII, Korea, and the early stages of the Vietnam conflict. Today, a mint-condition, original USMC-marked scope can sell for as much as $5,000. And with the current interest in vintage sniper rifles, just a working standard model Unertl scope in good condition can still bring $2,000 or more.
You're welcome.
It's one of the more interesting scopes I've seen on a relatively modern weapon, so I was interested in what it might be. Could be that that article I ran across that said it would be marked as a USMC model if it was an Unertl might be mistaken. Since it's a family heirloom, the value may not be as important as the heirloom aspect of it to you, but if it were mine, I'd still want to know what it was, even if for nothing else but insurance purposes.
Really cool piece though, regardless.
Blues