I picked up this 4 screw 18 yesterday, and was wondering if someone can tell me what year it was made,(k3942xx) I think '57 or'58. It's in excellent condition with the main wear being the turn line, but this will get shot, and hopefully soon. I did clean it, and removed the grips. The #'s stamped on the grips match except the last digit. The last digit on the grips is one higher then the # stamped on the gun. Was this just perhaps someone's mistake when it was put together? Thanks in advance.