Bump.. hoping someone has the cable and can check this. Thanks 😀

Joystick interfaces are very simple, there will be supply voltages on some pins and the rest will inputs which are what voltage happens when the pots are moved or buttons are pushed when given the supply voltages. So with it installed and a joystick test program running, you can find the supply voltages with a multimeter, and bridge those to each other pin with a 100 ohm resistor briefly and see which way it twitches in the test prog or which button it indicates was pressed. Then referring to that and the standard joystick pinout you've got your wiring diagram.

I know, I just didn't want to risk accidentally shorting pins on such a rare card.

I am raising this post from the dead only because the pinout was found thanks to the kindness of Full that was selling a diamond edge3d over at amibay. He provided me with the following pinout - hopefully anyone that is missing the adapter can recreate it 😀

Excellent! Thanks keropi. And thanks to Full @ Amibay for kindly providing it.

Updated the original post.