Usually MSI has W6156MS (Award Bios), A5169MS (AMI Bios) or P9245MS (Phoenix Bios) as Bios OEM message.
W6156VMS indicates a standard MSI-Bios for a MS-6156 with VIA chipset instead of intel chipset - this does not belong to OEM-ID.
The letters MS behind motherboard number represent standard MSI Bios (Retail board).
The letters MJ usually represent a special jumperfree version of a standard mainboard (Retail board).
Some newer retail Boards use MX instead of MS or MJ
I've seen MSI boards from OEM system builders/manufacturers using different ID-letters instead of MS/MJ/MX :
AE = Acer
C1 = Premio PC
C2 = CompuLink Research Inc
C3 = ???, possibly a Bios in simplified chinese language
C4 = ???, possibly a Bios in traditional chinese language
C8 = Compaq
D4 = Idot
E1 = Elonex
E7 = Gateway
E8 = ???
F1 = Fujitsu-Siemens
F2 = Pionex
F3 = Founder Computer
F4 = Fujitsu (old Fujitsu code, now Fujitsu-Siemens)
FA = 4MBO ?
FD = Fountain Technologies Inc, maybe now used by Pionex, too
G1 = Gateway
G2 = Gateway
G3 = Time Computers or Great Wall
H2 = ???
H5 = Hewlett-Packard
HA = Hedy
HB = Hyrican Informationssysteme AG
I1 = Ipex
I5 = Network (Media Markt, Saturn Hansa)
L1 = LG or IBM or LG machines built for IBM
L2 = ???
L8 = Lanix
L9 = Lemel
M2 = Hyrican Informationssysteme AG
M7 = Medion
O1 = Tiny Computers
O2 = Olivetti
O3 = Olidata S.p.A
P2-P7 = Packard Bell and NEC
SE = Seanix
SG = Suma (Korea)
T2 = Tsinghua Tongfang Computer
T9 = TriGem
TH = Phillips
V1 = Viglen
V2 = Vobis
Vobis Bios Support might come from www.maxdata.de as Vobis belongs to Maxdata for some years.
NEC seems to have bought Packard Bell ?
Tiny and Time Computers may have a close relationship,too.
Fujitsu and Fujitsu-Siemens are the same, at least in Europe
MSI Germany says Fujitsu-Siemens and Network allow to use Standard MSI Bios - Vobis , Peacock and Maxdata not .
For other system builders you have to ask their support .