Sega System 18
From Sega Retro
The Sega System 18 is an arcade system board released by Sega in 1989. The System 18 is primarily a soup-ed System 16, offering superior sound, more tile laters and extra graphics options.
System 18 boards had a very short run of games but most adhere to JAMMA standard, unlike previous systems. Most of these games also have the "suicide battery" as associated with Sega's System 16 hardware.
List of Games