SteveG
848
As I understand it,
first, according to Chuck Maddox (Moonwatch expert):
The c.321 is based on a design development project titled "27 CHRO C12" (27 mm diameter, chronograph,
with extra 12-hour register) took place in the 1940's by Albert Piguet and Jaques Reymond as a joint developement
project between Omega and Lemania. Launched in 1942, the 27 CHRO C12 later became known as the Lemania 2310,
or Omega c.321).
According to Bestfit, all the Lemania 12-ligne chronographs are based on the same original movement, the CH27.
These include both 2 register: CH27, 2300 through 2350, and 3 register chronos: CH27C12, 2500 through 2550,
some with incabloc shock protection. The Omega Moonwatch was a version of these latter
(3 register, shockproofed), and this series is still in use for the manual-wind chronographs of Breguet,
V&C (now discontinued?) and as you mention, PP (on its way out, as Swatch has indicated that future
product would have to be branded "Lemania" on the movement, among other reasons, presumably).
Some of this is illustrated in my article on the Lemania 2310 at
http://ninanet.net/watches/others02/Mediums/mlemania.html