IBM International Time Recorder Clocks
Most ITR serial numbers are a five- or six-digit number found stamped on the clock's punch mechanism, or 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 999999) and was restarted the next month, January 1950, at 10000. 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 whther it was the earlier or later year based on ithe clock's features and styling, such as casing (wood or metal), mechanical features (hand wound or electric) and function.
Serial Numbers
Up to 55000
55001 - 145000
145001 - 167000
167001 - 193000
193001 - 219000
219001 - 228000
228001 - 240000
240001 - 265000
265001 - 285000
285001 - 305000
305001 - 325000
325001 - 345000
345001 - 365000
365001 - 395000
395001 - 415000
415001 - 435000
435001 - 445000
445001 - 462000
462001 - 475000
475001 - 490000
490001 - 512000
512001 - 536000
536001 - 556000
556001 - 585000
585001 - 608000
608001 - 649000
649001 - 685000
685001 - 713000
713001 - 734000
734001 - 767000
767001 - 825000
825001 - 884000
884001 - 935000
935001 - 999999
10000 - 90000
90001 - 164000
164001 - 251000
251001 - 344000
344001 - 440000
440001 - 535000
535001 - 610000
Years
Prior to December 1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
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.