@@##@@ will be the next format but not until a few years from now.
There are reserved sequences on these formats, but the format remains the same for OCR purposes.
except a special format reserved for National Guard vehicles which is:
[G][N][R][BCEFGJLMPT]##
[G][N][R][BCEFGJLMPT]###
[G][N][R][BCEFGJLMPT]####
but not including these as they might not be relevant for most use cases.
tl;dr license-plates are typically composed of three parts. the city/
region where the plate was issued (one to tree letters) followed by a
random string (one to three letters too) and finally a random number
(one to four digits). the larger the city or region the shorter the
identifier they use. obviously having more cars to be registered, the
random letters and numbers are often longer/larger in those areas.
depending on the type of the car, implemented suffixes are:
H: Historic Cars / Oldtimers
E: Electronic Cards
wikipedia has a very long and detailed article which tries to explain
where all this comes from and why this is (still) needed:
https://en.wikipedia.org/wiki/Vehicle_registration_plates_of_Germany
