The Winchester Skeet chokes developed in the 1930's, and found on the Model 21, Model 12 and the Model 42 shotguns- were cut with a 17 foot radius- the conventional chokes were cut with a 13 foor radius- hence the "Bell shape" or ogive-- I have a 1938 Model 12 field grade 28 gauge with 28" solid rib barrel and it is marked WS-2 on the barrel--maybe a special order, maybe a factory Fubar, I don't know--

"The field is the touchstone of the man"..