Google images is showing me two variations of the Treasure the Chesapeake plate:
Is the top one the current one?
The style was switched in 2004. The top one is current. The bottom one is no longer issued, but can still be renewed and used. There's a $10 per year extra fee for that plate (so, $20 on top of reg. fees, since we have two year registration), which goes to some organization that promotes cleanup of the Chesapeake Bay.
On the original style, there were separate letter series for passenger cars (class A registration), SUVs/minivans (class M registration - multi-purpose vehicle - MPV - which is what the M signifies on crest plates), and light trucks like pickup trucks. I'm not sure if handicap or trailers were offered; I've never seen either. On the current style, the same series is shared between cars, MPVs, and light trucks, with separate series for trailers and handicapped plates.
The top plate is the passenger car/MPV/truck series (12345 B/Y, then 12345 C/B, then 12345 C/A, then 12345 C/C through the current 12345 C/G). The bottom plate is the MPV series (ABC-12D).
The original style also had an option to get a "BAY" number (123-BAY) for an additional ($50, I think) one-time fee, with the same option offered for MPVs (BAY-12A) and light trucks (1BY-234).
Original style:
Passenger cars: ABC-123 format
MPVs (SUVs and Minivans): ABC-12D format
Light Trucks: 1AB-234 format
Current style:
Passenger cars, MPVs, and light trucks: 12345 C/A format. The top letter is always C except for the original B/Y series that was issued. It was issued B/Y (for Bay), then C/B (for Chesapeake Bay), then C/A, then C/C forward.
Trailers: 12345 G/A format. The top letter is always G (because trailers are class G registration).
Handiacp: (wheelchair symbol) 1234 D/A format. The top letter is always D for Disabled, and we have just recently started the D/B series.