The divots were cast into some jaws (mostly closed jaw) for assembly orientation. One single pattern was used to produce both jaws which when assembled, resulted in the divots being on opposite sides when viewed in open position. This continued into some early ATC closed jaws (with dirt clearance).
At first glance, the V appears to be a foundry trademark which is cast into the piece. However, OC did their own casting and did not think it necessary to claim each part. This changed with ATC as they contracted all casting out to various foundries over the years since 1925. ATC required a foundry trademark or ID for performance-tracking (jaws, pans, swivels, etc).
If it were a foundry trademark, both jaws would be mirror image; so the V would remain right-side-up when placed in same position as opposite jaw. In the above pic that shows both jaws, with both Vs, you can see that the bottom jaw V would not remain upright when turned around to match top jaw...it would view upside-down. This indicates the marks were not cast into these jaws but done afterward for some reason.
My curiosity got the best of me and I have spent the morning looking at 44 jaws. I have found the same V, located in the same place on a pair of OC 44 Prop of US jaws; except the Vs are mirror image and remain right-side-up when turned around. This is a real mystery to me.