It looks like a Gyruss, but without the Manufacturer's imprints. Unfortunetly I'm not very versed in Gyruss boards, but doing a google search produced these few images:


Your small board looks to be bang on to the first picture. Right down to the KT-2304-2 serial.
Here's another pic:

In most of the pictures I've found, the Konami label is prevalent on the mainboard. But there were a few without, like this one (and the second one above):

Check out the
Gyruss page on CoinOpSpace, and
KLOV's page. There's a link to the manual and pinout sheet. Maybe you'll be able to get some hints there.
One thing that caught my eye was that Konami licensed Gyruss to Centuri when it came to US shores. Could Centuri have manufactured boards for Gyruss?
Best thing to do is ask questions over at the KLOV forums, or search for pages dedicated to Gyruss information.
Sorry I couldn't be more help.