Vintage Triumph motorcycle engine numbers are stamped into the case just below the cylinder on the primary side. Frame numbers are stamped into the frame on the headstock also on the same side. Crooked stampings and unequal depth are common. Frame numbers match the engine number after 1950, but may not have the model designation, only the numbers.
1938 to 1949 models
Year and model are stamped as prefix to engine number. For example 8-T-33445 is a 1938 Speed Twin (later identified as “5T” instead of just “T”). Frame prefixes were-”TH” for early Speed Twin. “TF” for the T-100 and later 1939/1940 Speed Twin.
Year stamped in engine number prefix with two figures. For example 40-5T-26445 is a 1940 Speed Twin. This practice followed religiously and some single prefixes may appear on postwar models. Frame prefixes were ‘TL” for the 3T up to 1948 and "TC" for 1949. TR5 for 1949 was followed by a "T” after the actual number. All other frames were "TF". TR5 models did not have separate number series but ran concurrently with all other models. I.E. 112671 was last 1949 TR5 and 113386 the last 1949 5T.
Note: All Grand Prix T100′s have letter ”R” suffix following engine and frame numbers. TR5 models had separate number series; engines from 101001 to 106424, frames from TC11001-T to TC13107-T. Starting in 1950 frame and engine numbers were matching.
| YEAR | ENGINE NUMBER | FRAME NUMBER |
| 1946 | From 72000 | Prefixed as before |
| 1947 | From 79046 | Prefixed as before |
| 1948 | 88864 - 102235 | TF 15001 - TF 25000 |
| 1949 | 102236 - 113386 | TF 25001 - TF 33615 |
1950 on FRAME AND ENGINE NUMBERS MATCH
| YEAR | PRE UNIT 500 / 650 |
|
| 1950 | from 100N | |
| 1951 | 101NA to 15808NA | |
| 1952 | 15809NA to 25000NA | then 25000 to 32302 |
| 1953 | 32303 to 44134 | |
| 1954 | 44135 to 56699 | |
| 1955 | 56700 to 70929 | |
| 1956 | 70930 to 82799 | then 0100 to 0944 |
1957 FIRST UNIT CONSTRUCTION 350 / 500
| YEAR | UNIT 350 / 500 |
PRE UNIT 500 / 650 |
| 1957 | H1 - H760 | 0945 to 011115 |
| 1958 | H761 - H5484 | 011116 to 020075 |
| 1959 | H5485 - H11511 | 020076 to 029363 |
| 1960 | H11512 - H18611 | 029364 to 030424 |
| then D101 - D7726 | ||
| 1961 | H18612 - H25251 | D7727 to D15788 |
| 1962 | H25252 - H27932 | D15789 on |
1963 FIRST UNIT CONSTRUCTION 650
| YEAR | UNIT 350 / 500 |
UNIT 650 |
| 1963 | H29733 - H32464 | DU101 to DU5824 |
| 1964 | H32465 - H35986 | DU5825 to DU13374 |
| 1965 | H35987 - H40527 | DU13375 to DU24874 |
| 1966 | H40528 - H49832 | DU24875 to DU44393 |
| 1967 | H49833 - H57082 | DU44394 to DU66245 |
| 1968 | H57083 - H65572 | DU66246 to DU85903 |
| 1969 | H65573 - H67331 | DU85904 to DU90282 |
TRIUMPH ALPHA NUMERIC SYSTEM STARTS 1969
In 1969 Triumph introduced a new system of numbering engines and frames. There are two letters, a five digit number, and a model designation. The first letter represents the month, the second the model year, and the number which began at 00100 for each model year.
PLEASE NOTE THE MODEL YEAR
Each model year usually started in August and ran until July of the next year. The year of manufacture is the model year. For example: PD32232 TR6R would be a 1970 TR6R manufactured in November of 1969, and KE16670 T120R would be a 1971 T120R manufactured in September of 1970. The letter "V" after the model designates a 5 speed gearbox.
| MONTH OF MANUFACTURE | YEAR OF MANUFACTURE |
| A = JANUARY | C = 1969 |
| B = FEBRUARY | D = 1970 |
| C = MARCH | E = 1971 |
| D = APRIL | G = 1972 |
| E = MAY | H = 1973 |
| G = JUNE | J = 1974 |
| H = JULY | K = 1975 |
| J = AUGUST | N = 1976 |
| K = SEPTEMBER | P = 1977 |
| N = OCTOBER | X = 1978 |
| P = NOVEMBER | A = 1979 |
| X = DECEMBER | B = 1980 |
Knowing the year of your engine is important when ordering parts. If your engine was made in 1971 but is a 1972 model year you may get the wrong parts if you are using a 1971 parts catalog. Please be sure of your engine year to insure correct orders.
Of course there are exceptions to the guidelines, and these are only provided as a guideline and to help identify Triumph engines and engine parts.