* [`clueboard`](https://github.com/qmk/qmk_firmware/tree/master/keyboards/clueboard) ← This is the organization directory, there's no `rules.mk` file.
* [`60`](https://github.com/qmk/qmk_firmware/tree/master/keyboards/clueboard/60) ← This is a compilable keyboard, it has a `rules.mk` file.
* [`66`](https://github.com/qmk/qmk_firmware/tree/master/keyboards/clueboard/66) <-- this is also compilable, it uses `DEFAULT_FOLDER` to specify `rev3` as the default revision
* [`66`](https://github.com/qmk/qmk_firmware/tree/master/keyboards/clueboard/66) ← This is also compilable- it uses `DEFAULT_FOLDER` to specify `rev3` as the default revision.