Anyone know how these things work?
NI registrations are issued by the DVLNI, a kind of regional parallel government agency of the DVLA. I bought my first car in Belfast and subsequently brought it back to England, and that required the registration to be transferred from the DLVNI to the DVLA when I moved.
The first letter is a serial letter (ie issued A, B, C etc until all possible combinations run out). The second two letters indicate the county of registration. The four digits are issued sequentially; three digit numbers and obviously desirable ones (1111, 2222, 1234 etc) are withheld for cherished sale.
The county codes are:
AZ Belfast
BZ Down
CZ Belfast
DZ Antrim
EZ Belfast
FZ Belfast
GZ Belfast
HZ Tyrone
IA Antrim
IB Armagh
IG Fermanagh
IJ Down
IL Fermanagh
IW Londonderry
JI Tyrone
JZ Down
KZ Antrim
LZ Armagh
MZ Belfast
NZ Londonderry
OI Belfast
OZ Belfast
PZ Belfast
RZ Antrim
SZ Down
TZ Belfast
UI Derry City
UZ Belfast
VZ Tyrone
WZ Belfast
XI Belfast
XZ Armagh
YZ Londonderry
QNI Cars with indeterminate age, kit cars.
There is, therefore, no indication of vehicle's age in an NI registration.
To give an example, Bath bus depot has had two recent arrivals from Belfast, one of which is RKZ 4760. What would this mean?
Not much. It was first registered in County Antrim.