This is a rare box used by World Class Service and repair centers to test Super Nintendo systems. It plugs into the cart slot and has cables to both controller ports and the video port. When powered up the software in the tester checks video signals, clock timing, internal memory, and controller data. After that it runs a series of tests like sprite mirroring, scaling, transparency, and music channels. The entire sequence runs about 2 minutes. The box itself has Super Famicom labelled on top, but works in a USA NTSC Super Nintendo system. There is a button to select which video output to check (RGB, S, VIDEO) and a button to test which clock to check (CIC, SYS, 21M). The clock output goes to an RCA socket which would most likely connect to something like an oscilloscope. There are also buttons for BACK and NEXT. The NEXT button is used during the video test when prompted. The colors of the case are much closer to the NES than the SNES. Gray bottom is slightly lighter, tan top is slightly darker. Overall this one is in very good condition with no visible damage and no yellowing. The board inside is labelled as SNS-TEST A-01 1991.