I bought my Centennial Centaure sometime around 1965 give or take a couple of years. Serial # is 28XX.
It does have proof marks and notched recoil shield. Cylinder plain with no roll markings.
Top of barrel is marked - Centennial trademark "1960 NEW MODEL ARMY".
It has a rearing Centaur logo on the left side, but both rear feet are on the ground, not rampant by the heraldry definition.