Need to ID a Williams scope mount for a handgun.

[CHEVYINLINE6]

While poking around in a tall cabinet looking for the instructions for a unused pistol safe and I found a new in package Williams handgun scope mount model MK-D-B. Code # 20198. I must have bought it for a Ruger 22 auto with a bull barrel. Any idea what this fits for sure ? I just found the same one on eBay. It appears mine is missing the bushings to properly mount it. I looked under Williams sights and it was on the second page.
Thank's,
CHEVYINLINE6.