Tasco 4 x 20, vintage information.

I have a Tasco scope, 4 x 20, 1 inch tube, about 8 inches long. It has a flat block made with the barrel of the scope, attached underneath. This mates with a 1 piece mount. , that fits weaver bases, attached to the flat block with 3 screws. There are slots in the solid side of the mount that allow the cross bolts to be slid forward or backward to position the scope, or to adjust to the base spacings. Scope is made in Japan, very heavy for its size. I am guessing it is an AR scope, but can't find a picture or any information about it. It is a silver finish, says pm4x20BA japan A-58 5. Has 4 inches, or more eye relief. Does anybody know anything about this scope. Curious what the original price was, approximent value now.

http://i.imgur.com/PUdZp.jpg


Integral rail, too long for an AR...…… but I don't remember seeing these on the market (since the 1960's, anyway)