Originally Posted by rurak
What's the difference beyween a mk I , ii , or iii?
Biggest differences are the 1 did not have a bolt hold-back feature after the last shot. The 2 added a slide release that locks the slide open after the last shot. The 3 changed the mag release from the heel on the 1s and 2s to a 1911 style mag release. The 3 also got new "saftey" features like a loaded chamber indicator and a safety that will not allow the gun to fire without a mag.
There are other smaller changes, but those were the biggest changes.