Old Bushnell, bottom post widens to inverted V when clicked on?

Anyone ever see this? 

I can grab it tomorrow but passed last weekend. It’s Japanese glass, 3x9x40. Decent shape. I literally thought I broke it when looking through & feeling magnification ring movement. In front of it is another thin steel ring. When you turn it a positive click is heard and the bottom post thin crosshair expands to a thicker inverted V. 

He was asking $25 & I could have gotten him lower but I wanted a dozen Port Orford Cedar arrows for $10. Arrows are great though 6 need tips or fletching.

I need to know if this scope is rarer than average. I’ve never seen one. Anyone?