This is a used API 500-6B HC Lunchbox in excellent condition.
The API Lunchbox 500-6B can hold and power up to 6 500 Series modules. Universally acclaimed, the API Lunchbox was originally designed to receive API’s own 550a, 550b and 560 EQ, 512c mic preamplifier, the 525 and 527 compressor modules but took the world by storm with many manufacturers adopting this extremely convenient format to bring unique and great sounding modules at a more affordable price.
Note modules are not included and are listed separately.