A better idea would be to introduce a nurismatist shop/stall in Eldevin who will let you use these coins to buy decent low-level equipment.
This should be a useful resource for new players, would provide a reason to spend time fishing in the fountain early in your game-life, and wouldn't upset any economy.
As a by-product, it would be easy to introduce a value-difference for the various coin-types.
- Trillium likes this