Splendide Coins are coins that are earnt thought completing certain quests from various NPCs. some of which are repeatable while others can only be done once per character
Completeing the following quests will give you Splendide Coins
(Will make this a table once i have tried all ways)
Twenty Five From Two Tribes Quest (One Time)
Coins can currently be used by going to Splendide and heading north to a fairly big building. in the building will be an NPC called Merchant of Splendide (You will need the Ring of Wise Kings to talk to the npc) . you can exchange one Splendide Coin for of a choice of three foods. Pinguicula's Fruit Jam , Luciola's Honey Jam and Cornus's Tears.