This is a Vivitar 70-150mm MR Matched Multiplier. I believe this device doubles the focal length of the Vivitar 70-150mm zoom. It's optics are optimized for that lens. This is a 4-element multicoated lens made in Japan. This item is new-old-stock. The condition is mint except for some aging evident on the leather case (leather pealing back on one small spot).
Price: $15 plus shipping