Most ITR serial numbers are a five- or six-digit number found stamped on the clock’s punch mechanism, on its case, or on a label inside the clock. By using the chart below you can determine the year the clock was first shipped from the IBM factory, most likely the one located in Endicott, New York.
This serial numbering system ran through December 1949 (ending with 999,999) and was restarted the next month, January 1950, at 10,000. This means a clock with a serial number of, say, 228,000 may have been shipped in either 1921 or 1952. In such instances you can usually determine whether it was the earlier or later year based on the clock’s features and styling, such as casing (wood or metal), mechanical features (hand wound or electric), and function.
Note: The last time clock shipped in December 1949 had the serial number 999,999. In January 1950 the serial numbers began repeating, beginning with serial number 10,000.
IBM International Time Recorder Serial Number Chart
| Year | Serial Numbers |
|---|---|
| Prior to December 1916 | Up to 55,000 |
| 1917 | 55,001 – 145,000 |
| 1918 | 145,001 – 167,000 |
| 1919 | 167,001 – 193,000 |
| 1920 | 193,001 – 219,000 |
| 1921 | 219,001 – 228,000 |
| 1922 | 228,001 – 240,000 |
| 1923 | 240,001 – 265,000 |
| 1924 | 265,001 – 285,000 |
| 1925 | 285,001 – 305,000 |
| 1926 | 305,001 – 325,000 |
| 1927 | 325,001 – 345,000 |
| 1928 | 345,001 – 365,000 |
| 1929 | 365,001 – 395,000 |
| 1930 | 395,001 – 415,000 |
| 1931 | 415,001 – 435,000 |
| 1932 | 435,001 – 445,000 |
| 1933 | 445,001 – 462,000 |
| 1934 | 462,001 – 475,000 |
| 1935 | 475,001 – 490,000 |
| 1936 | 490,001 – 512,000 |
| 1937 | 512,001 – 536,000 |
| 1938 | 536,001 – 556,000 |
| 1939 | 556,001 – 585,000 |
| 1940 | 585,001 – 608,000 |
| 1941 | 608,001 – 649,000 |
| 1942 | 649,001 – 685,000 |
| 1943 | 685,001 – 713,000 |
| 1944 | 713,001 – 734,000 |
| 1945 | 734,001 – 767,000 |
| 1946 | 767,001 – 825,000 |
| 1947 | 825,001 – 884,000 |
| 1948 | 884,001 – 935,000 |
| 1949 | 935,001 – 999,999 |
| 1950 (series restarts) | 10,000 – 90,000 |
| 1951 | 90,001 – 164,000 |
| 1952 | 164,001 – 251,000 |
| 1953 | 251,001 – 344,000 |
| 1954 | 344,001 – 440,000 |
| 1955 | 440,001 – 535,000 |
| 1956 | 535,001 – 610,000 |