Korg A3 SPC-03 General Purpose Card. It will also work with the Korg A2.

Background:
The Korg A3 was a programmable, studio-quality guitar effects device made in the early 1990s, and was popular with many recording artists, most notably The Edge from U2. Korg's ROM (Read-Only-Memory) cards were manufactured for the A2 and A3 series by Korg and by third-party makers. The A3 card series included new chains and effects beyond the twenty chains that were originally available, giving you an additional 100 programs onboard. They simply plug into the slot in the front of the A3. These cards are no longer manufactured, and have become very rare.

This particular card, the SPC-03 General Purpose card, expands on the original internal programs, with effects designed for specific instruments. There's enough new chains and sounds in this A3 card to keep you busy for a long time!