Something Gengen said on another thread made me think this may interest some.
Licence plates here have a leading letter and then some numbers.
The letter denotes what classification the owner of the vehicle is.
A and B are for government vehicles, but I don't see As much - think they're Ministerio del Transporte. See a lot of Bs.
C, D, E are reserved for embassy vehicles. I think D is Diplomático, C - Consular and E for everything else.
F - Fuerzas Armadas.
K is for vehicles owned by foreign firms or individuals with temporary residency (working for foreign firms, I think) so you can see these on HGV lorries, trucks and cars.
M is for Minint - Ministerio del Interior.
P plates are seen commonly - Particular - denotes the vehicle is registered to a private individual.
T - another that is well known - Turismo
U - these are on electric motorcycles and also the triciclos. Not sure if the same is used for electric cars. Don't see them often and can't remember/didn't notice.
On petrol bikes, there are P and R. I don't know why some are R.
S, W and Z are recent introductions for religious institutions, co-operatives and other non state organisations. I have only seen about three Ws so far and one I took as religious because it also had an icthus insignia.
The only letters that aren't used, are I, O and Q, so the ones I haven't mentioned are in use somewhere. Maybe allocated by government department.
If anyone can add G, H, J, L, N, V, X, Y, that would satisfy my transport code curiosity.
Also an explanation on P vs R on motorbikes.