Well, I had an idea, so I just browsed through a website that lists a lot of wacky designs for that sort of tool and I found a close match, but I l'll pm you the answer so other people can enjoy guessing.
"Regular pliers with small jaws could be used to set a tooth. Designers added to this to make pliers with a built in stop (Fig. D). The stop is usually adjustable and rests against the saw blade as the jaws bend the tooth. The goal of the stop is to make a consistent set and prevent tooth breakage. Depending on the style, the tooth is either gripped first in the jaws and then bent or the saw set is aligned to the tooth and the jaws closed."