The term used for the images shown in the 1922 V-C catalog is "micrographies", which I translated as Xrays. Not sure the same word exists in English. It's what you see through a microscope. But in any case, a very close look at the composition of the steel used in V-C barrels. And I think we can take it to the bank, given the direct references to Holtzer steel, that that was indeed the source V-C was using as of 1922--whether they made the barrels themselves or whether Holtzer made them.

There is absolutey no question that V-C makes barrels now, and has for quite some time in the post-WWII era. I'd agree with Raimey that it's not entirely clear when they started doing that.