Finnish coins have a letter on them, but it is the initial of the Mint Master's (nowadays the mint's Chief Executive) surname and does not refer to the mint itself.
It has been reported that the current MM will be retiring in March of 2008, and the search for a new CEO is hoped to be completed before the turn of the year. Perhaps this is so the mint will know what initial to put on coins for 2008?
A part of me is curious, however, to see if the new practice of adding "FI" and/or the Mint's logo on foreign coins will replace the tradition of using the Mint Master's (which as mentioned before is now a CEO) initial on domestic coins. I doubt it will but one never knows.
