i have a 127 which i believe is a mk1 has two slots on the end of the barrel,the front sight slides onto these and is tightened by a screw.the trigger on this model is plastic.in the case of the mk2 the trigger is meta li think.from memory i think the front sight on the mk2 has inter-changeable elements which the mk1 lacks.there are more enlightened fwb enthusiasts on here than me and they will probably fill in any gaps.or correct my comments. atb.