Despite what has been said above, for some reason my MKI and MKII will use all of the magazines I have and it doesn't seem to matter. The MK 1 mags hold 9 and the MKII mags hold 10. I find I can use them interchangeably. Maybe I am just lucky. Here is my stable of MKI & MKII pistols. The MKI is at the top without the bolt hold and with a tapered barrel if you have trouble identifying them.
I do not own a MK3, so I can't speak to that.