013-0055-00
The Tektronix 013-0055-00 Plug-In Extension is used for calibrating and repairing Tektronix 530, 540, 550, and 580 series oscilloscopes as well as their plug-ins..
This particular extender is optimized for the 580 series, which has its pin-out flipped 180° over earlier 5xx series. Pins 8,9,11,14,16 are connected via 93 Ω coax; these pins are signal and trigger lines on the 580 series, but are mostly power pins on the earlier series.