Wow, please keep me informed on this one, I am definitely interested.
If I ever do a personal coin it will be a Phacops Rana.
I might use a coprolite for a personal . I used to have one sitting on my desk... I passed it around the class and even used it as a hall pass. After a few weeks of the kids bugging me about what it was out came the poem...
A hundred million years ago
A Dinosaur felt the urge to go..
It strained with all its might
and out popped this coprolite.
The look on their faces was great...