Transparent Guitar
Dan Erlewine at FRETS.COM
Dan's special demo Clear Guitar

OK, it's not really playable, but it is the coolest instructional tool ever:
It's a regular dreadnought style guitar with acrylic top and back plates. The perfect thing for demonstrating repair techniques! Dan made up this guitar by screwing the top and back onto the sides. That way he can take it apart to change the bracing style, or whatever.

Dan gives a few intonation pointers to Buzz Feiten:

See how easy it is to visualize what's going on:

Clamping a brace from the outside while seeing what's going on inside:

Demonstrating magnet techniques:
