Only marking on this is "KEX" Patent Pending. KEX comes up on Google with tire repair tools but nothing on history or anything like this. Very strong spring (takes 2 hands squeezing hard to open) opens jaws a little bit and release makes it grab tight. The golf T you see grabbed in it is about as big as it will go, so maybe 3/16" max, much smaller than valve stems. If it said Bell System I would say it's a linemans wire pulling tool? Anyone?