Yes, a long branch sniper chest will fetch even more than a British chest. In fact, you might be able to make an owner very happy. I started a registry of the 90L rifles and scopes over on the milsurps forum. A user named DaveM has that rifle, although his scope is not the matching scope. I have sent him a PM on that site....he may try to contact you. I know if I had the rifle, I certainly would.
By the way, I work in a museum, and I can tell you that the curator and the conservationist would leave that chest alone.