Coin of Exchange Wondrous item, rare (requires attunement by a spellcaster)

This polychromatic coin of magical quicksilver seems to suddenly shift in form and material between passing moments. It is an alchemist’s parlor trick, a marvelous play of magic and material, made possible by an infusion of potent magic.

The coin of exchange is typically produced in small batches, often as many as 1d6+4 coins when successful, and can be safely stored and carried in a regular coin pouch. The coin is capable of far more than meager sleight of hand, and can transform at the command of a capable spellcaster. You can use an action and speak a command word to activate one of the coin’s special properties. Additionally, for the duration, you can use a bonus action and call the coin, or a weapon coated with it, back into one of your free hands, from up to 100 miles away as long as it is on the same plane as you. At the end of the property’s duration, flip a coin. On tails, the coin becomes unstable as it melts away and is destroyed. On heads, the coin returns to its original form.

Switcheroo! Flip a coin of exchange and catch it in a closed hand. You concentrate (as if concentrating on a spell) and visualize a similarly sized coin that you know, and the coin of exchange’s material, shape, and form is transformed into the coin that you visualized for up to 1 hour. If a creature uses an action to interact with the coin, it can make a DC 15 Wisdom check, recognizing it as a counterfeit on a success.

Liquid Plating. You touch the coin to a nonmagical weapon, coating it with the magical quicksilver in its unstable form. For 1 minute, that weapon becomes a magic weapon with a +1 bonus to attack rolls and damage rolls.