MODEL VERSION A       US MKT - ROAD (1960) B       US MKT - COMPETITION (1960) R       US MKT - ROAD (SOME YRS UK) RT      US MKT - ONLY 750 MADE (1970) C        US MKT - COMPETITION V       FIVE SPEED GEARBOX E       CONFORMS TO US ENVIRON. REGS. ES     ELECTRIC START D        BONNEVILLE SPECIAL (1979-1980) TSS    EIGHT VALVE ENGINE TSX     US STYLE CUSTOM LE      LIMITED EDITION ROYAL (1982) AV     ANTI VIBRATION (POLICE FRAME)

YEAR C       1969 D       1970 E       1971 G       1972 H       1973 J        1974 K       1975 N       1976 P       1977 X       1978 A       1979 B       1980 KDA   1981 EDA   1982 BEA   1983

MONTH         YEAR        SERIAL #        VERSION       X                A             123456                E

Meriden  Bonneville

SERIAL NUMBERS

T120  650cc 1958 - 1972

T140  750cc 1973 - 1983

In 1969 Triumph changed to a new lettering system as follows

First prefix letter        indicates month of  manufacture

Second prefix letter   indicates model      year

Suffix letter                indicates model      version

source: The Classic MotorCycle - 1997

PREFIX  LETTERS             SUFFIX LETTERS

MONTH A      JANUARY B      FEBUARY C      MARCH D      APRIL E      MAY G     JUNE H     JULY J      AUGUST K     SEPTEMBER N     OCTOBER P     NOVEMBER X      DECEMBER

2 prefix letters, followed by serial #, then followed by suffix letter

Early  T120's  have a six figure serial number

Duplex framed pre-unit  T120's are prefixed D

Single downtube pre-unit T120's  prefixed DU

Single downtube unit  T120's are prefixed DU

( 1958 - 1960 )  020076 to 030424

( 1960 - 1962 )  D101 to D20308

( 1963 )   DU101 to DU5824

( 1963 - 1970 )  DU5825 to DU90282