ROM-Only boards
Some of the last arcade boards made by SNK Playmore around 2003 were standalone NeoGeo systems with no cartridge slots. Three games are known to have been used on that kind of hardware:
PCB models: MV0, MV0BR, MV0C
Particularities
All game ROMs are encrypted. Some boards have ROMs on SMD sockets for some reason.
The power amp is class D.
The MV0C board used for The King of Fighters 2003 uses an Altera CPLD labelled "MASK2".
Chips used
See [this list] for board scans.