Although it is uncertain as to what this Performance tester was used on, it has a flip up chip insert for what appears to be a high density VLSI chip which would be a departure from Atari normal chip packaging, so far noone from Atari's CED or HCD divisions had been able to indentify this tester and its use until recently when an actual Atari 800XL design with an entirely new chip onboard was found, called the Atari 800XLCR, codenamed "KERI" after its new chip by the same name which is a combine Antic/GTIA chip referred to as the CGIA was found, this new motherboard explains the term "Keri" and now explains the use of the above test fixture, yet another piece of the puzzle has been found and more questions answered.