Without getting too much into method: with most coin bending routines, you can't let the spectator sign the coin that is bent. Or, you have to switch out the first coin for a coin that is pre-bent (meaning, before the trick begins). Or, you have some sort of secret, hidden device in your hands or up your sleeves. BREAK has none of those things, so it's as pure and simple as I can imagine a coin bend possibly being.
The coin can be freely examined and signed, on both sides, by the spectator. The coin is then visually BENT and broken at your fingertips. There's nothing else in your hands. You can do it in short sleeves. You can do it naked, if you're into that. In the end, you're left totally clean, and the spectator can keep the signed pieces. They'll remember it forever.