From the SailNet's Morgan mailing list:
Hull Numbers

i.e.: MRY26001M79A-461

MRY = Always same.
This number is assigned by USCG.
Identifies the builder as Morgan.

26 = Code Number for model (see below).

001 = Hull Number (must be three digits).

M = Always same. No significance.

79 = Model year (starts August 1).

A = Month scheduled to ship (see below).

- = Always put this dash in.

461 = Model Number (see below).

ModelCode NumberModel Number
OI-2801282
OI-3302333
OI-3603361
OI-4104413
M-2205222
M-2706271
M-30/207303
M-33T08334
M-36T09362
OI-4110414
Classic 30011304
M-2212223
M-2713272
OI-5114511
Classic 25015253
Jungle Boat16400
OI-4917491
OI-3718371
OI-37MKII19372
OI-3020305
OI-4121415
M-3822382
M-4523452
NA-4024402
Moorings 4625461
M-3226321
M-4627462
OI-5128512
OI-33MS29335
M-3930391
OI-4131416
OI-36MS32363 (only one built)
M-3833383
M-3234322
M-6035601
M-4636463
Moorings 6037602
M-3838384
M-3239323
M-4540453 (racing version)
M-4541454 (cruising version)
M-3642364 (racing version)
M-3643365 (cruising version)
M-6244621
M-3645366 (update of 364)
Moorings 5046501

MonthCode Number
AugustA
SeptemberB
OctoberC
NovemberD
DecemberE
JanuaryF
FebruaryG
MarchH
AprilI
MayJ
JuneK
JulyL