All the vintage Ludwig legs I have that went with their American made drums only have the knurling (or crosshatching on the older ones) in a band near the top of the leg (regardless of whether they are the 17" "short" or 23" "long" version). That band is about 4-5 inches wide (I don't have one handy to measure just now but they are all the same). These legs were/are all 3/8ths inch (9.5mm) in diameter.
Newer "classic" Ludwig legs seem to only come in the 23" size and the knurling on those seems to cover about double the length compared to the old ones. Not sure when that change took place. Various other lines such as the Rockers/Accent/Element/etc. generally used imported generic legs, often with a wider textured area and sometimes 10.5mm diameter rather than 9.5.