I just got a second Wollensak Vitax and now discover my first one is not what I thought.
The first is the brass one in the pic below. It's 4 1/4 inch diameter always made me think it was a number 5, according to the 1913 catalog.


But yesterday I got a number 4, and it's smaller. It's 3 1/5 in diameter and it's 13.5 inch focal confirms it's a number 4.

I went and looked again at the brass one, it reads "Vitax Portrait Lens No 2." It also has a 13.5 inch focal length (measured from studio shutter to ground glass). Did Wollensak reduce the size of their Vitax petzvals at some point? The configuration seems changed too, the FL is shorter than the later 4 1/2 in diameter Vitaxes. In short, the brass No. 2 is the largest listed for diameter, but middle for FL.