history book
Bikes using frame numbers starting with 49 used lightweight Metal Profile (MP) telescopic forks from 1950
Some very early bikes had WEBB type pressed steel girder forks

Roughly 1949~1953/4

1949/1953 MP forks

  Bikes using frame numbers starting with H56~H60 used DOT's own leading link forks. These used a cast link from 1956 until the new version in 1962.
Some bikes still used the Earles forks into 1956

The only machine to use a different code was the road going Mancunian, it used M56#### for all of its production run, regardless of year of manufacture

1956~1962 CAST link forks

width British Hubs

full width Alloy hubs 1959

Full width Grimeca Alloy hubs circa 1959


British Hubs were used as supplies dictated


49#### Rigid DOTs with 6E Villiers
51#### Brockhouse sv 250cc bikes          1951/1953
H53#### Swinging arm models from late 1952 until end of1954
H55#### Minor mods to frame in 1955
H56#### Frame used the 9E Villiers, no rubber engine mountings, used up to 1958
H58#### Twin engined bikes
H59&H60#### used until early 1962
 H59 includes some twins
Bikes using frame numbers starting with H53  used DOT's own design of Earles Type forks.
NB the standard fork was still the MP type Earles type being the option

Roughly 1953~1954
For 1955 ~1956 the dampers were a single piece chrome cover

Note that frame numbers  up to H531121 used a different head stock bearing later frame numbers

Though you could have specified MP forks instead


1953~1956 earles forks   From 1962 an all new frame and forks machine was introduced, using a modified front forks and spring steel links.

The frame used a square section tube along with round tube for the forks

nb Very early models did use cast links

1962~1968 Spring link forks

SQUARE FRAME 1962~1968

Though possible to get later square frames with MP telescopic forks circa 1965

MINARELLI trails 1968
These used REH front forks

First letter of the frame number
A = 1962
B = 1963
C = 1964 etc etc
As in AA 0123
Second letter is a month identifier, but you need to know the code to work it out.
Best bet is to contact the club and for a fee they will produce an A4 wp letter listing the bike's credentials

The number is just a serial number
There should also be a letter T for trials  or S for Scrambles just to the left of the main frame number