This Bower ring comes with a aperture ring for the mount end of the lens.
I've added an aperture scale.
The ring was also further modified by adding a 49mm male filter thread to the 55mm ring for use on 55mm and 49mm threaded lenses.
Reversed, directly on the camera, 50mm lenses yield an image reproduction ratio of approximately 1:1.3 or an image size of approx 30X20mm on the APS sensor