Here is a example of how the file naming scheme is #A#A-14G###-AA
# = Number / A = Letter
The first 4 characters appear to be the year it was released and model it was released for, with 5U5T being the newest currently
the second 6 characters are the type of file it is, apps, maps, voice, map_voice, gracenotes etc
APP = 14G381
VOICE = 14G391
NAVIGATION VOICE = 14G422
GRACENOTES = 14G423
MAPS = 14G421
RADIO LOGOS = 14G658
LICENSE = 14G424
UTILITY = 14G386
the second character of the last section is just a version number essentially, So AC for example is China 1.16 27/07/17 and AD is China 25/08/17, the letter is simply incremented for newer versions on the same year, see below sections for explanation of the first character of the last section
Voice - 14G391
A = ARW,CZC,DAD,DUN,ENG,FIF,FRF,GED,ITI,NON,PLP,PTP,RUR,SPE,SWS,TRT
B = ARW,DUN,ENA,ENG,ENI,ENU,FRC,FRF,KOK,MNC,MNT,PTB,PTP,SPE,SPM,THT
C = ENU,FRC,SPM
D = ENA,ENG,ENU,GED,MNT,PTB,RUR,SPM,TRT
E = ENU,MNC,MNT
F = ARW,DUN,ENG,ENI,ENU,FRC,FRF,MNC,PTP,SPE,SPM,THT
Maps - 14G421
A = China
B = EU
C = US
D = ANZ + SA +TW
F = CAM, India, Israel Mena, SAF and SEA
Navigation Voice - 14G422
A = CN (ENU,MNC)
BA = EU (DUN,ENG,FRF,GED)
BB = EU (DAD,FIF,NON,SWS)
BC = Possibly CZC,PLP,RUR
BD = EU (ITI,PTP,SPE,TRT)
CA = NA (ENU)
CB = NA (SPM)
CC = NA (FRC)
D = ANZ (ENA,ENG), SA (ENU,PTB,SPM), TUR (ENG,GED,RUR,TRT)
CZC - Czech
ARW - Arabic
CZC - Czech
DAD - Danish
DUN - Dutch
ENA - Australian English
ENG - British English
ENI - Indian English
ENU - American English
FRC - Canadian French
FRF - French
GED - German
ITI - Italian
KOK - Korean
MNC - Chinese Mandarin
MNT - Taiwanese Mandarin
NON - Norwegian
PLP - Polish
PTB - Brazilian Portuguese
PTP - Portuguese
RUR - Russian
SPE - Spanish
SPM - Mexican Spanish
SWS - Swedish
THT - Thai