A friend of mine lost a fin from his South Coast board. I am trying to help him find a replacement. Does anyone have Ideas? It is an ACE fin, 4.25”base x 5.5” height, which is mounted in a fin box. The fin has a tab about 3/8” to ½” deep. This tab has a relief slot cut into one side, which runs front to back for about ¾ of the tab. The fin sits in the box and is held in place by a stainless tab tightened in place by a stainless screw. http://www.indygoofyfoot.com/images/bernies-fin.jpg 
I’m guessing that must be an old board. I can ask around in OB but I’ve never seen a fin exactly like that. A replacement could be hand-made, plenty of guys here who could do it. I don’t know that you’ll be able to buy one, unless you get lucky and there’s one sitting in a box at South Coast or something. If you didn’t want to start from scratch you could grind down a bigger fin… Ace has been making boards for a long time (he makes a lot of multi-fin boards, 5 fins, 6 fins) and some of the fin sets become a little rare over time, I think. PS - since you have a picture of the left fin, you need a right one - right?
You’re assumptions are correct, it is from a six fin board and we are looking for the right hand mate. If it’s rare in San Diego can you imagine trying to find one on the Great Lakes…? http://www.indygoofyfoot.com/images/bernies-fin.jpg
Ok, I have the picture of your lost fin and will see if I can find one this weekend. Don’t get your hopes up yet, though.