Greener Police Shotgun from Hong Kong

Hi folks,
Does anyone know what round the Hong Kong Greener police shotguns were chambered for?

I know the Egyptian Police used a special catridge but I can't find anything online as to what the Hong Kong police used.

I've been offered one and haven't handled it yet but I've been told that the receiver is marked "Greener Mark II" and "HKP 6xx" and is also marked with a .719" , a 12 in a diamond, 2 7/8" and 4 1/4 tons (PSI).

I'm hoping it'll take standard 2 3/4" 12ga rounds (because I don't want the hassle of having special rounds for it).

Thanks in advance for any info.
Cheers,
Dreadnought1

The markings described were for the standard 12 gauge of the time. Regular 2 3/4 inch shells should work just fine.

Richardwv,
Many thanks! I'll be picking it up next week.
Cheers,
Dreadnought1