Prior to WWII there existed an ‘old’ and ‘new’ system for marking ordnance laid down in AP 1243.

The old system was as follows:

All service bombs painted yellow with a red band around the nose denoting that the bomb is filled. A plain green band with no fraction or other marks indicated an 80/20 Amatol filling. A plain green band with a fraction below indicated an Amatol filling of that fraction. A plain green band with the word ‘Trotyl’ stencilled on the green band in three places indicated a TNT filling. This system applies to all stocks filled prior to January 1928.

A new system was introduced for uniformity between Admiralty and War Office production. All H.E. bombs (Amatol, TNT or Baratol) were painted yellow overall and marked as follows:

A red band around the nose denoted the bomb was filled.
A green band around largest diameter of the bomb denoted filled with Amatol or TNT.
A white band above the red denoted the bomb was S.A.P.
A white band either side of the red denoted the bomb was A.P.
Stencilling was also applied.
Bar 10/90 or other fraction below the green band in three places denoted the bomb was filled with Baratol.
The word Trotyl on the green band in three places denoted the bomb was filled with TNT.
80/20 or other fraction below the green band denoted the bomb was filled with Amatol.
G.P. 120lb or other nomenclature round the body between the red and green bands denoted the nomenclature of the bomb.
I or other numeral around the body between the red and green bands denoted the Mark of bomb. W or other initial or trademark around the bomb between the red and green bands denoted the name of the firm or filling station.
25/2/27 or other date around the body between the red and green bands denoted the date of filling.
1234 or other number around the bomb between the red and green bands denoted Lot. No.of filling.
118lb or other weight around the bomb between the red and green bands denoted the actual weight of the bomb complete with vanes but without components.

During the war the colour of the casings was changed to dark green.