Old style threads as used on all pre-Mark III "J" frame guns.
This includes all Pre-War Colt's and the "E & I" frame guns.
I can't find my spec sheet, but I "think" this is the same thread used on ALL "D" "E & I" Colt revolvers.
Barrel threads: .5634-32
New style threads as used on recent production Python's AND on the Trooper Mark III/King Cobra, including all "J" "V" and "AA" frames.