omg this quest doesent give 50 gil lol quite the contary it gives u a WATER ORE i repeat a WATER ORE!! 50 gil would be a waste of a quest and it also takes ton of fame in bastok to do this quest :)
I really don't know why there are 3 posts here wondering what this item is, the description and links are quite clear, but I will try to elaborate since for some reason people can't make heads or tails of what they are seeing.
As can see by the BOLD NEON WHITE LETTERS on the left hand of the description, it is a KEY ITEM.
Also, as you can see from the USED IN QUESTS links on the right(also in bold neon white), you can see that it is part of the quest "Groceries". One can assume that it is a key item that you recieve during, from or after the quest "Groceries" by this link association. One should go to that link for further information.