Boyle Fiberschritt Round Glass Cutter German Made Clock Repair

Description

Found in my late father's clock repair shop on a work bench, so assuming he used it to customize glass for clock doors and bezels. I don't know much about it and had no idea what it was until I looked it up online.
Boyle Fiberschritt German made round glass cutter. From the ones I came across, others have a round ball part at the end with another long brass part attached to the ball (whatever it is called) and this does not have those pieces.
I assume it can still be used without it but please use your own judgment.
Has rubber suction pad that attaches and releases from the glass by flipping the lever. Has minor wear like a few oxidizing on areas of brass measure stick, some scratches and dings from use. I see no major damages. When black lever is pushed up, the round piece opens about ⅛" and when the knob is pushed down, it closes tight. The brass measuring stick part measures just about 8" and the round black piece measures 6 ⅞"  circumference.