Norma. They come in nickel plated cases.

In Australia I roll my own. I would like to have tried some factory loads but rare indeed.

To sure why the Norma factory loaded Ammo for the 375 Flanged Mag is nickel plated whilst their component cases are not. Fortunately I have a reasonable supply of cases, plus some nickel ones a great member sent me with a gorgeous leather rifle sleeve for my H&H double rifle.