If it's real wavey use a bit that has the shank of the router bit on top if it's not to wavey use a bit that has a top bearing on it.
It will run on the side of plaque and should give you a nice edge.
This is a job for the router table.
Don't go to slow with the shank type router bit it will burn the edge.
If you are creating a modern looking plaque you can use an ogee, round over or chamfering bit with a bearing on the end. For an antique looking plaque use a rotary surform tool in a drill press or a simple round wood rasp or file to create uneven semicircular cuts along your edge. See example here: http://routerforums.com/showpost.php?p=10879&postcount=3
Let us see the finished product.
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