Engine number prefixes - Identification

B40FT B40 Military - 1965
B40GA WD B40 Australian Army MK 1 - 1967
B40GB WD B40 British Army MK 1 - 1967-70
B40GN WD B40 British Navy MK 1 - 1969 - 70
B40GR WD B40 British Air Force MK 1 - 1968 - 70
B40M B40 Military MK 2 - 1968-69
B40GD WD B40 Danish Army MK 1 - 1967-68
B40GD WD B40 Danish Army MK 1 - 1969-70

For civilian production machines, from 1969 onwards date prefixes were added. But this did not apply to production WD B40 machines - evidence shows only late production factory spare engines used this lettering.

The first letter denotes the month:

A January
B February
C March
D April
E May
G June
H July
J August
K September
N October
P November
X December

The second letter gives the year from August to July:

C 1969
D 1970
E 1971
G 1972
H 1973
J 1974