Should it be a dovetailed back? Or just a regular 13 rounder with sig mark? It’s quite hard to find new or like new dovetailed sig mags in the market. Thanks!

I don't know what gun laws are like in your country, but if there is no capacity restriction, then yes, it's the 13-rd German dovetail mags. Over here, it would be the 10-rd dovetail one, since it was during the Klinton AWB era.

Oh- so it means I have to get the dovetail? Even if mine is KG or mid 90s manufactured?

We don’t have restrictions here with magazine capacity. Just bought 15 rounder mecgars here on sale but previous owner lost oem magazines

You asked, "What’s period correct magazine for a KG date code P228?"

And the answer is the dovetailed mag. You want to get it, fine, but you don't "have to" anything. The 15-rd Mec-Gar mag works perfectly fine. I'd say it's better, because it's just as reliable, but you never have to worry about the seam coming apart at the top like you would with the dovetail.

I found a NOS zipper back that’s German made in the packaging this is for what model? Mine has exeter importer mark.

"zipper back" mags were for year 1989(JK), 1990(KA) and 1991(KB) P228s.

Thanks! Will look for a dovetail back..