Kimber's 'Series I' 1911s do not incorporate a firing pin safety. This feature is required by law in certain states. The new 'Series II' pistols do incorporate this feature, and are legal for sale in all 50 states. Some states also require new pistols to be furnished with a piece of spent brass. All series II weapons are accompanied with this.
Many folks who enjoy working on 1911s prefer the Series I pistols, much like they prefer a pre-Series 70 Colt 1911. One less hand needed when reassembling the weapon.
'
Series II' pistols do incorporate this featureInteresting. Series I aren't legal for sale in California, so the one I got is a Series II, and the box was marked as not for sale in New York. Hmmmm.