If my memory is correct, between 1980 and 1982 I owned an 8” .22 LR Colt MK II. I bought it in 1980 or 1981. It is only its Mark number I’m unsure of. I think MK IIs had sintered metal parts and replacing the sintered metal with better steel was the most important upgrade in the MK IIIs. I had indeed forgotten all later MK numbers. I haven’t been following Colt revolvers since selling the long tom .22. The only Colt revolver I own is a 1910 Officer’s Model Target .38 special. I just think it's neat because it's my oldest revolver. So can one of you Colt lovers tell us about Colt MK IIs evolution into MK Vs?