The User's Review: Vivitar 2X Macro-Focusing Teleconverter (with Minolta M/MD Mount), Released in 1981

These converters with different mounts for various brand cameras are specially-designed for both macro and tele shooting. Cool! Mine has a Minolta M/MD mount. As I tested, once I extended the barrel on the converter, it worked only as a macro device, and turning the barrel also did focusing besides the lens' one.

The converter comes with two covers for both ends and a case. Its original price was $79.95 as the prince tag marked on the box. For the new converters with different mounts, their prices might be close. However, my online search show that the used converter with KAR mount (with 7 pins, for both Pentax KA and Ricoh P) is more expensive since it can be easily used on Pentax DSLR with manual focusing.

The two scales in blue and white are for 50mm lens
set at the closest and infinite focus distances 

They can be used with lenses or zooms, but its manual is needed for how to convert the parameters. Therefore, I scanned the manual and posted it here.