The Sinister Shekel appears to be an ordinary silver coin ($10) minted by the Company of Goldsmiths in the city of Tredroy.
However, each of these coins have been cursed.
So long as the coin is in a character's possesion, that character receives a 1 point penalty to any die roll they make in the game.
This lasts until the character scores some notable success despite the bad rolls (GM's descision), then both the "Sinister Shekel" and the success turn to ashes, and the curse is ended.
The Sinister Shekel can be given away at any time, however it is unlikely that the character will realize that the coin they carry is cursing them.
A mage might detect that the coin is enchanted in some way if held (roll vs IQ+magery-1), as will a successful "detect magic" spell.
However, a successful "analyze magic" spell will detect the curse.
Cost to Enchant: $40 (Value = $0)
Aventure Hook: The Sinister Shekel