The serial number is stamped on the tailstock end of the bed between the flat- and v-ways. It is used to determine the size and type of lathe, plus any special features or attachments. The earliest records show that lathes were numbered sequentially, beginning with 700, in July, 1910, and ending with 186,514 March, 1947.
After that date, a new numbering system added a three letter code to indicate 1) the swing, 2) the gear and apron combination and the location of the drive, and 3) the spindle hole size, type of swing, and special features.
For example: "2345" "RKL" "7"
is the 2,345th 10" lathe built. It has quick change gears, friction feed apron, and underneath motor drive, a large spindle hole, and standard swing. The number 7 is the model number, which is changed when modifications are made to the machine that do not change the overall characteristics. Each swing size begins a new numerical series, starting with the number one.