This is a cartridge shell for use with Commodore 64s and 128s, and works with a specific dead test cartridge (and any other cart based off the PCboard that project uses) linked below.

If you like to work on old Commmodore 64s, you've probably heard of a "DEAD TEST" cartridge..  If you've not heard of this- this is essentially a diagnostic program, created by Commodore themselves, for testing/troubleshooting C64 boards.

Use a “DEAD TEST” cartridge circumvents a few things (I think the Kernal and BASIC ROMs?), and allows a C64 with issues in those items to start.  It then tests the CPU, RAMs, and other chips (including the SID) and helps you to verify whether they're ok or if they have a problem.

Here's where you can buy the actual “DEAD TEST” cartridge (just the electronics):
https://www.ebay.com/itm/161406355942

Here's the manual:
https://drive.google.com/file/d/0B5ZJg5sBZdeJZF9mdklDY21XUHM/view?ts=5633d25d

I didn't make this cartridge..  I didn't even design the cartridge shell file!  (I got that from here:  https://www.thingiverse.com/thing:3498853)...  I merely printed this, then after using my "engineering compensation tool" (-aka- Dremel) so that it would fit with this circuit board, I went back and updated the .stl files so no adjustments are necessary- simply print, put the cartridge circuit board in place, find a screw that works, and you're all set.

I printed with PLA, used 50% rectilinear, and each piece took about an hour using my Prusa i3MK2/S clone, otherwise using generic PLA/normal settings.  

MANY MANY thanks to Peter Holly, who shared a fantastic design- I think I only needed to re-work it so that it would fit my specific circuit board (linked above)..  Thanks Mr. Holly!!!

Jason