I don’t advise you should use farthings and livres tournois and weighing scales (at least not all the time), but it might be interesting to have some goodies hidden in treasure chests. So here’s what I’m going to do, with the help of +guillaume jentey +Gherhartd Sildoenfein and +Cathia Remond.
There is 1% chance per 100 GP value that some coins found in a treasure hoard are of special interest.
Special coins (d20)
1. Half of the hoard is fake (fool’s gold or silver plated lead).
2. d100 coins are cursed. They can only be parted with in exchange for nothing.
3. One coin is fake and hollow. It contains a tiny scroll with a message.
4. A portion of the hoard is from an unknown or lost civilisation. A lead to an adventure site?
5. d6 coins are ancient and worth 100 times their value to a collector.
6. One coin is blessed by the saints of commerce (get advantage on a negotiation or trade related roll, once a day).
7. d3 coins are magical (function as scrolls, roll randomly).
8. Cheater’s coin with heads on both sides (of different rulers).
9. Anti missile talisman coin. It catches a missile attack, that destroys your purse and/or backpack along with its contents.
10. One lucky coin: reroll any die. The coin disappears along with d6 tenths of your overall fortune.
11. Half of the hoard is marked by a criminal organisation (spend it at your own risk).
12. The whole hoard is cursed by the weight of greed (counts as double encumbrance).
13. d100 of the coins are minted with a player character’s face.
14. Half of the coins are from an enemy kingdom. Careful where you spend them!
15. The most precious coins come from the underworld. They are worth three times as much as long as they stay away from direct sunlight.
16. d100 coins are rare, known, and stolen.
17. All silver coins are Moon Money. Their weight and value double at night.
18. One of the coins is cursed : This shinning coin becomes the owner’s most valued belonging, he/she will cherish it more than his/her own life.
19. 2d10 untarnished, sparkling coins, all linked together by magic. While one of them is still on your person, they appear back in your pocket on the next dawn (leaving the purse of whoever got them).
20. d4 jingling coins: they make stealth almost impossible while mixed with other coins.