I would guess that its intended for placement on pliers that came without grips. I have a Dunlap and Craftsman brand pair that came without grips. I guess "back in the day" that you could buy grips for them. Now you can't! Cool little find!
I have tons of very old channellock dating back to the early vintage years and they all come without any grips; Wish I could find boxes of those old handles I would be set as they say!