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BSA used a system of letters and numbers for yearly identification of their machines. This information combined with the yearly numbers book (coming soon) should help you identify the year and model of your machine.

As with all listings of this type there will be mistakes. However, hopefully, they will be few and far between.

It should also be borne in mind that these listings are given in BSA seasons. This ran, generally from the August in the previous calendar year through to the factory shut down in at the end of the following July. Therefore the 1953 BSA season ran from August 1952 through to July 1953.


Identifying your machine.

First, a word of caution to anybody buying a machine, particularly if it does not have any documentation or proof of origin. If you are not satisfied then do not buy as mistakes can prove expensive later. Remember buyer beware.

If documentation is available then check the details against the machine. On most BSA's the frame number is located in the following places. It is always stamped, raised numbers are casting part numbers. Up until 1968 it is rare for the engine and frame number to be identical and where the frame is shared by several models the codes start with the smallest model e.g. all A series models have A7 or A50 prefixes with the exception of the Rocket Gold Star and Super Flash.


Pre war
On the front top frame member either by the front seat stay or by the steering head.

On the front down tube below or in front of the petrol tank. The exception is the early Bantams where the frame number is between the front engine mounting plate. These are usually faint and small.

By the steering head reinforcing plate or front down tube. Some Bantams on the engine mounting plate, these sometimes break and re-welding obliterates the stamping.

Usually on the front engine mounting lug.

1968 onwards
Front engine mounting lug but the engine and frame numbers are the same.

1971 oil in frame models
Steering head stem. The oil in frame B-series are stamped on the propstand bracket


Engine markings

Engine numbers are easier to find usually by the crankcase mouth on the primary side. Exceptions are the Bantams which could be stamped on the front mounting point or just behind the crankcase mouth.

This is just a guide and will fit most situations but frames were legitimately restamped by dealers if the original was damaged and a replacement fitted. These could be stamped anywhere and often were not stamped at all!



Owners with late model BSA's can easily identify the month and year of their machine as the factory adopted a dating system for frame and engine numbers for the 1969 season models.

As with all previous BSA seasons the model year started after the factory shutdown in July so that 1969 models were those made between August 1968 through to July 1969. They would however have some machines in stock so that it is possible that a July model may be to either the previous or the next year's specification.

The code consisted of three parts, the first as two letters giving month and year respectively, the second was a five digit number and the third a model code. The engine and frame received the same markings. After dating and identifying many thousands of BSA's we have found that often a bike was built or shipped outside the dates given by the lettering system so this should only be used as a rough guide to the year and month of your machine. Advertiser - Click here for a visit!
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The date letters are as follows :-

1st letter : 2nd letter
A January : C 1969 Model
B February : D 1970 Model
C March : E 1971 Model
D April : G 1972 Model
E May : H 1973 Model
G June : J 1974 Model
H July :  
J August : To avoid confusion F.I.O. and L were
K September : not used, although it is easy to confuse
N October : letters C and G.
P November :  
X December : Advertiser - Click here for a visit!
Specializing Vintage British Motorcycles. Specialty Parts for BSA B50,B44 and B25`s.

The numbering started at the beginning of each season and always started at 00100 leaving the first 99 for experimental use. The numbers were consecutively allocated throughout a model range so as an example all B group machines were lumped together irrespective of whether they were a B25 or B44. From experience in crossreferencing machines against the factory despatch books of which the club have a copy, we have found that in about 50% of cases the bike was not despatched according to the date of the lettering. Sometimes they were despatched months earlier or later so the lettering system should just be taken as a rough guide.

The model designations are as follows. The years given are all model years:-

A Series

Rocket Three A75R through all years.

Rocket Three five speed A75RV 1969 and 1970

A75V 1971 and 1972

Royal Star A50R through to 1970.

Thunderbolt A65T through all years.

Police Special A65P through all years.

Lightning A65L through all years.

Firebird A65F 1969 and 1970.

A65FS 1971.

Lightning 750 A70L 1972.

Note in 1972 the frames for the twins were marked A65 with no model designation, from XG.00101.A65 on.

B Series

This is a bit complicated!
Starfire B25S Sept 1968 to 1970.
Gold Star 250 B25SS 1971.
Victor 250 B25T 1971.
Fleetstar B25FS through to 1971
Victor Special B44VS 1969 (C) November 1968 through June 1969
then 1970 (D) July 1969 to July 1970
Shooting Star B44SS 1969 (C) November 1968 through August 1969
then 1970 (D) July 1969 through July 1970
Gold Star 500 B50SS 1971 to 1972
Victor 500 B50T 1971 to 1972
Victor MX B50MX 1971 to 1973

D Series

D14/4 Supreme D14/4 1969 part

D14/4 Bushman D14/4B 1969 part

B175 Bantam D175 1969 to 1971

B175 Bushman D175B 1969 to 1970


other points to remember


Early post war machines up to Z series had the frame stamped similar to the plunger or sprung frames e.g. YA7.R. 9999. (The 'R' meaning RIGID). Also this carried through to some but not all of the engines.



1966 'A' series machines started the season with A50, A50B and A50C frame designations with the usual non-matching engine markings. After frame 3200 the engine and frame markings were the same. There was a short period where the engine marking matched the frame marking but the frame prefix was A50. Presumably to use up stock in store prior to the change over.

Machines still in stock in the 1967 season (about 1000) were resold in the 1969 and 1970 season. These returned machines are shown with a cross at the beginning of the despatch book record, they then reappear at the end of the book with the revised despatch date. The 1969 models are identified by the adding of an extra 0 at the end of the frame marking putting the number series into the 100,000's.

Machines re-exported in 1970 were stamped with a 'Y' suffix to indicate that they were 1970 models and therefore eligible for the increased warranty.


The C15 Sports Star 80's and B40 Sports Star 90's engine markings were often abbreviated to CSS and BSS respectively.


A second series of letters and numbers starting ERS means that the unit has been replaced under the factory Exchange Replacement Service and the figures are the despatch record number.

These lists have been compiled from numbers listed in the parts books from 1930 until the factory closed in 1973 and from known bikes up until 1930. The list was compiled painstakingly by the club's Librarian Steven Foden, with editing into HTML by Shane Phelps. If you know of any discrepancies please email us. Advertiser - Click here for a visit! Advertiser - Click here for a visit!
BSAOC 1997, 1998, 1999, 2000. All rights reserved. Advertiser - Click here for a visit! Advertiser - Click here for a visit!