The reason I think there may be more sizes out there is the numbering sequence. Also the fact that older wrenches often had overlaps, ie. the same sizes on two different wrenches. I have some overlaps and missing No's.
My No's are 1214, missing, 1618, 1820, 2022, 2224, missing, 2628, missing, 3032. So, I think there should be a 1416, 2426 and a 2830. The 1955 catalog I have does not list the wrenches I consider missing, but does an older catalog list them?????