I'm not saying this is the case, but remember that the Vacuum-Grip pattern was owned by Forged Steel Products, and although they were the OEM for Snap-on, they continued making their own pliers - with the exact same grips, through the mid 50's, even after 1949, when they were finally "bought" by Snap-on. (Quotes because the relationship was always a little funky, with Forged Steel Products helping to bail Snap-on out when they were in financial straits in the late 20's, becoming a Blue-Point factory, and their founder became the President of Snap-on!) I don't know if they made pliers for others though. And if that is 1959, then almost certainly "pure" Snap-on at that time.