You also mentioned that the used acetone had a lot of residue. Since acetone evaporates quickly, there is a decent chance that some of the residue redeposited, even before you got it in the distilled water. I would strongly recommend using the 2 soak method, where you immediately rinse the coin in a second bath of clean acetone. You can still use distilled water after this but it's not necessary. You can also check the cleanliness of the acetone by putting a few drops on clear glass. If there is residue left when it evaporates, it may be time for an acetone change (especially if it's the second rinse)