Loads for Greener 12/14 Gauge

Suppose this may get a pass with it being a surplus police shotgun.

I recently picked up a Greener Martini action shotgun in their 12/14 gauge or whatever they called it. Barrel looks like new although the exterior has seen better days. I read they saw service in Egypt which explains the hard life.

Has anyone loaded ammo for one of these? I found Rocky Mountain Cartridge makes the brass and the loading kit but haven't been able to find any good load data.

I can see that the gun was nitro proofed either for or with 1 and 1/2 oz shot.

Thanks.

They take a special shell and not a normal type. This way only Police will have the ammo for it. I think it was Sarco that use to have loaded surplus ammo for it. Not cheap and very hard to reload.