0110PD9201 R06/19

Legacy Date Code System

1956–1995 Date Code System

The date code system shown below was adopted in 1956 and was in use on all distribution equipment and circuit breaker products, until June, 1994. The only exception was high-volume QO™ circuit breakers. In some cases, this system is still used today.

**    
A — January   A — 1950, 1971, 1992, 2013 N — 1962, 1983, 2004, 2025 Example: Q12150 Circuit Breaker dated July 28, 1950, 1971, or 1992, Operater/Shift 1

B — February   B — 1951, 1972, 1993, 2014 P —1963, 1984, 2005, 2026
C — March   C — 1952, 1973, 1994, 2015 R — 1964, 1985, 2006, 2027
D — April   D — 1953, 1974, 1995, 2016 S — 1965, 1986, 2007, 2028*
E — May   E — 1954, 1975, 1996, 2017* T — 1966, 1987, 2008, 2029
F — June   F — 1955, 1976, 1997, 2018 U — 1967, 1988, 2009, 2030
G — July   G — 1956, 1977, 1998, 2019 V — 1968, 1989, 2010, 2031
H — August   H — 1957, 1978, 1999, 2020 W — 1969, 1990, 2011, 2032
J — September   J — 1958, 1979, 2000, 2021 X — 1970, 1991, 2012, 2033*    
K — October   K –1959, 1980, 2001, 2022 Y—1971*    
L — November   L — 1960, 1981, 2002, 2023      
M — December   M — 1961, 1982, 2003, 2024      
NOTE: The letters “I”, “O”, and “Q” are not used in this date code system.

Variations of this date code system in use:

  • Month and year only; ie BA

  • Month, day, and year; ie. B20A

  • Month, day, year, and shift; ie. B20A2

1950–1955 Date Code System

Between 1950 and 1955, the method below was used to date code load centers, safety switches, and some circuit breakers manufactured in Detroit, MI.

Month Year Operator Number
A — January X — 1950  
B — February Y — 1951 Example: Circuit breaker dated June, 1955
C — March Z — 1952
D — April A — 1953
E — May B — 1954
F — June C — 1955
G — July  
H — August  
J — September    
K — October    
L — November    
M — December    

Merchandised distribution equipment and molded case circuit breakers are date coded to identify the time of manufacture. This code is useful in tracing equipment having design changes and in pinpointing areas and assembly periods. The date code is placed separately or hand-stamped directly onto the device, and should not be confused with label numbers, etc. This information applies to all circuit breakers and distribution equipment.

IMPORTANT: Always obtain the date code when investigating a complaint on any device.

Pre-1950 Date Code System    

Two methods shown in the diagram below were in use prior to 1950. It cannot be determined as to exactly when and where these methods were used; however, this information in conjunction with the equipment appearance and years in service should enable a date of manufacture to be determined.

 
Month Year Operator Number   Month Day of Month Year Operator Number
A — January A — 1928     S — 1 D — 7    
B — February B — 1929     Q — 2      
C — March C — 1930     U — 3 C — 8    
D — April D — 1931     A — 4 O — 9    
E — May E — 1932     R — 5 M — 0    
F — June F — 1933     E — 6      
G — July G — 1934     Example: Circuit Breaker dated January 22, 1934, Operator 22
H — August H — 1935    
I — September I — 1936    
J — October J — 1937    
K — November K — 1938    
L — December L — 1939    
  M — 1940     Example: ML1 Circuit Breaker dated either December 3, 1954, or January 23, 1954, Operator 720
  N — 1941    
  O — 1942    
  P — 1943    
  R — 1944    
  S — 1945    
  T — 1946    
  U — 1947            
  V —1948            
  W — 1949            
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