TT, the first abbreviated system came from Mike Orlen because it has the "Choke & Chamber Music" Logo at top of page. I cannot remember where I got the "New System". It is copied out in longhand at bottom of the photocopy of the Orlen photocopy and I remember it being called "New System". Possible I got it from Browning or Remington website. I checked again and the Orlen chart does use Sk1 and Sk2 nomenclature rather than Sk in and out. I can't explain why the two skeet constrictions bracket ic in the Orlen chart but are both less than ic constriction in the other. I don't know the constrictions of the Winchester designations for solid chokes. I have always heard that they are much more open (less constriction) than their nominal counterparts in Browning solid chokes.
jack
