Raindrop Coin  

Checking on the quest Memorial of Power learns that it is
initiated by examining a Memorial Purse which drops from monsters
in the Fallen Gate and not by the questreward Raindrop Coin
from the quest cleansing the filth.

On examining the questreward Raindrop Coin you get the following:

This ancient coin is no longer used
as currency anywhere in Norrath. A
Merchant may be willing to buy it
from you, however.

Image is uploaded as reference.