But this seems clear. The 30mm chronometer movements were the Calibers 30T2Rg, 30T2RgSc (small seconds and centre seconds respectively) which were later in 1949 renumbered to Cals 262 and 281. The chronometers used special parts, including the hairspring, balance wheel and pallet lever and in addition had a fine regulation device (hence the 'Rg' in the original 30T2Rg etc calibers). The screw regulator seems only to have been used on the 30mm movements (the manual winds discussed here and their bumper automatic equivalents). The later movements, for example the ones used in the Constellations, appear all to use a swan-neck regulator.
sub second:
30 : 15 jewels, no shock protection
30T1: 15 jewels, no shock protection
30T2PC: 15 jewels, Incabloc
260: =30T2 since 1949, 15 jewels
261: 17 jewels, antimagnetic
262: 17 jewels, excenter regulator
265: 15 jewels, antimagnetic
266,267: 17 jewels, antimagnetic
268: ring- instead screw balance
269: flat- instead Breguet-hairspring
sweep second:
30SC : 16 jewels, no shock protection
30T1: 16 jewels, no shock protection
30T2SC: 16 jwwels, no shock protection
30T2SCPC: 17/18 jewels, Incabloc
280: =Omega 30SC T2 since 1949, 17 jewels
281: 17 jewels, excenter regulator
283,284: 17 jewels, antimagnetic
285: ring- instead screw balance
286: flat- instead Breguet-hairspring