RAS, The Mountaineer scope was Leupolds early internal adjustable model. Made in 4x & 6x from the early 1950's until around 1960, when it was superceded by the M7 scope. They are 1" tube & nitrogen purged, but not constantly centered reticle as with the M7.
They rarely come up for sale, but recently a NIB example was auctioned & went for over $200 dollars, IIRC. A 4x Mountaineer is the scope mounted on Jack O'Connor's favorite Model 70 .270 Winchester, rifle No.2 I believe.
Edited by 3dtestify (02/16/11)