The handles on that pair of pliers appears to be a cellulose acetate type material such as Tenite. I've seen a number of older pliers that have used that type of material for the handles both on US made, and European made pliers. It's possible the handles were a variation of the pliers that was available to purchase in addition to the regular ungripped pliers. It's also possible the handles were added aftermarket by the owner. Klein still sells replacement Tenite grips that can be added to their pliers. Ideal also sells replacement Tenite grips for pliers. My understanding is that some electricians prefer the Tenite because of durability and the textured surface. The Klein and Ideal handles have different grip patterns that neither match each other, or the grips on those pliers, but there were like other patterns back when that material was more common. As far as the patterning on the steel plier handles, it was probably just easier to manufacture the same base pliers and add handles when an order came in for the acetate handled version.