There are occasions when blocks of serial numbers have been manufactured out of sequence, sometimes years later. Ruger does not necessarily produce firearms in serial number order. It can be used to determine the approximate year your Ruger firearm was It is not necessarily the very first serial number shipped, but This number should be used as a point of reference The above chart shows the approximate first serial number shipped for (manufactured from 1955 to 1973) Caliber: 357 Magnum
