I can give you the run down on UK plates , and there meanings (location of first registration)
plates started as 1 a , going to 999 a , then 1 b to 999 b , this carried on , we do not use I O Q or Z
at 999 y , they then went 1 ab ,,,
on and on till we had got to 999 yyy
then they reversed them and started again
after 2001 they came out with a new system
i will find you a link later
an average 1950 s bullet would have sumething like 951 PYK (example)
note that ft numberplates were banned in the UK in the early 80,s , older bikes however can keep there plate,
they were commonly known as pedestrian slicers