qmk_firmware/keyboards/ploopyco/trackball/rev1_005
..
config.h
keyboard.json
readme.md
rules.mk

See the main readme for more details.

This is for the R1.005-R1.006 version of the Classic. It's easily distinguishable from the R1.007+ versions of the Classic because it has an ATmega32u4 on the board.