カメラレンズの前に付けて超望遠にするアタッチメントです。
単眼鏡としてつかってもすぐれたものでした。

Another "7" item for the month.

This is a 7x35 monocular/7xTelephoto attachment for SLRs.
It attaches to the front of a standard lens of any SLR
and work as a telephoto of 350mm in focal length.

It has a quality optics as a monocular also.
This was advertised in the '60s and early '70s magazines.