Molex78802 Module
This is a 3d-printable plastic carrier and matching empty PCB template to fit in the carrier, and both together fit in the option-rom socket in Tandy models 100, 102, 200, & 600. (and any other machine that has that same socket, such as Epson PX-4 & PX-8)
If you want to build a REX or Teeprom, visit those pages and order the pcb from OSHPark, and order the carrier from Shapeways.
If you want to start a new design based on the same PCB and carrier, clone the github repo, and open the included files in kicad for the pcb and freecad for the carrier.
Currently, the freecad file for the carrier is not very useful as a "source" file. It's just a mesh pretty much the same as the stl file for printing. Re-drawing the model from scratch in either freecad or openscad is planned. Then that will be a more useful source file for the model to make future changes from.
Pics: https://photos.app.goo.gl/zynHU4LSpd5BZBYC9
Sources: https://github.com/aljex/pcb2molex8878
Carrier: http://shpws.me/RngB