Vehicles constructed before 1.1.73 may display traditional style "black and white" plates i.e. white, silver or grey characters on a black plate.
Lettering must be of a set size. It must conform to one of the two groups below.

Characters	Group 1	Group 2
Height	89mm	79mm
Width (except the number 1)	64mm	57mm
Stroke	16mm	14mm
Side margin	25mm	11mm
Top & bottom margin	13mm	11mm
Space between characters	13mm	11mm
Space between groups	38mm	33mm

There are additional arrangements if the vehicle is a motorcycle or tricycle

Traditional number plates fitted to vehicles manufactured before 1 January 1973 are not required to display the mandatory character font, but the characters must be easy to read.