From your description, I agree with lens_hacker - this adapter interposes between the lens and camera body and allows rangefinder focusing with parallax compensation between approx. 1 meter and 50 cm. The adapter came in various models, SOOKY (or Part No. 16502), which accepts a collapsible Summicron in its collapsed state and is for screw-mount cameras, SOOKY-M or SOMKY (16507), same as above but for bayonet-mount cameras, and SOMKY-M or SOMKY-UOORF (16509), like SOMKY which accepts the head of a non-collapsible Summicron. An entertaining accessory if it is not too expensive and you already have the appropriate lens and camera!