ROM-Only boards
Some of the last arcade boards made by SNK (Playmore), they are standalone NeoGeo systems with embedded games instead of having cartridge slots.
Particularities
The encrypted game ROMs are labelled with their NGH number and data type, like in cartridges but without any manufacturer numbers.
The audio power amp is class D.
Chips used
Those boards are known to use the NEO-YSA2 audio subsystem chip, NEO-GRZ graphics chip, NEO-PCM2, NEO-CMC (90G06CF7042 / 90G06CF7050) and NEO-PVC banking chips.
See [this list] for board scans.