Here's an interesting one. This is a Maxon AD-900 that I've had for a very long time I think I bought it back some time around 2006 or 2007. One of the things you'll notice in the 4th picture is "Reversed Polarity" written on a piece of tape. The reason for this is right after I bought the pedal the AC adapter quit working it was next to impossible to find a replacement so for a couple of years this thing sat around without any use until a friend of mine flipped the polarity so that it could be used with any 12V adapter. This made it incredibly easy when using a power brick because this wouldn't have been possible at the time without having to have extra space for a 12V adapter just for this pedal. This can be easily "un-reversed" by simply swapping the wires going from the board to the plug. I can show the wires but didn't feel like opening this thing up. Please let me know if you would like pictures and I can do this.

Cosmetically there are a ton of scratches on this thing but it works exactly like it always has.