The "Mitakon MC ZOOM 35-70mm 1: 3.5/4.5" lens is a Continuous sharp lens with 52mm Filter size. At f3.5 it proposes much better than many others of its kind. I purchased the lens together with the Nikon F-301 on Ebay for 29 euros.
The mechanics of the zoom is stiff!
The optical quality is a little flat. The relationship with the focus and blur is good. The photos looks surprisingly good.