Honest Abe
From AmtWiki
An illegal weapon technique, supposedly used as a tactic against sluffing.
In consists of placing a loose penny beneath the cloth cover of a sword. The penny can be slid up close to the grip where it can be held in hand, thus giving the weapon the appearance of being perfectly safe and legal, but it can also be release and allowed to slide to the tip where it can provide a painful sting on a hit.
This is an illegal tactic, using this will get the weapon and probably the person thrown off the field. It should never be used.