Maxchinery's Handbook;
"Vanaddium Steel ordinarilly contains from 0.16 to 0.25% vanadium. The effect of Vanadium is to increase the tensile strength & elastic limit, & it gives the steel the valuable property of resisting to an unusual degree, repeated stresses. Vanadium steel is ewspecially adapted for springs, car axles, gears subjected to severe service, & for all parts which must withstand constant vibration & varying stresses."
Chrome Vanadium alloys were given a 61xx SAE number. They would appear to be great alloys for a double "Frame". I personally can se no reason to associate them with the success of the Parker Bolt Plate.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra