Serial numbers can be found on the back of the chassis. Letters tell you the name of the product and if the chassis belongs in a head or a combo. The numbers tell you the year of production, the month of production and the production number.
A 65 Amps London without serial number is a super early production that Dan Boul and Peter Stroud made out of their garage.
(Name) (Head/Combo) (Year) (Month) (Number)
King's Head Head
Royal Albert Head
Lil' Elvis Combo
Rocket 88 Head
Stone Pony (= "75") Combo
Apollo (no combo's were made)