OK, I think I've figured out the point system, and while I hadn't found the exact coin I intended to use as the challenge, I did find an alternate that should work just as well.
In fact, the alternate option even allowed me to add a separate bonus...

British Indian Ocean Territory, 2 pounds, 2012
Life of Queen Elizabeth II series - Queen Mother
KM#7,
Numista 69618 (their photos are even worse than mine, alas)
I sometimes use this coin (or the other one) as a silly trick question: how many different people are featured on it?
The answer (in this case) is 2 - Queen Elizabeth II and the late Queen Mother.
However, Elizabeth II shows up three times - with three different portraits.
Which leads us to the challenge...
Post your coin (or token, or medal) with the most portraits of the same person!
1 point for each
different portrait of the same person, not counting the first; only one person per coin eligible
0.25 points for each
identical portrait of the same person, not counting the first, up to a maximum of 4 points; portraits that differ only in size, and/or that are mirror images of each other, count as identical
0.1 point for each portrait of a
different person, not counting the first, up to a maximum of 2 points
0.7 points for each
different portrait of a person who was
not used for the 1 point entry, not counting the first (of that person), up to a maximum of 5 points total or 3 points per person
0.05 points for each
identical portrait of a person who was
not used for the 0.25 point entry, not counting the first (again, of that person), up to a maximum of 2 points total or 1 point per person
Bonus: 0.5 points if the coin's issuing authority has a permanent population of 1000 or less; 0.1 points extra for 100 or less, 10 or less, and 1 or less, cumulative
...All of the above, obviously, applies to any
single coin (or token, or medal). Multiple entries (if any show up) would count separately.
I'm not yet sure if I should allow the 1 point and 0.25 point entries to count for different people. I doubt that it would come up, anyway.
The challenge coin would count for 2.9 points (2 for the three different portraits of Elizabeth II, 0.1 for the Queen Mother, and 0.8 for the bonus). I am sure that it is possible to go much higher.
For the record, while I'm willing to allow tokens, medals, or other exonumia (as they're likely to have a much wider variety of multiple portraits), issuing authorities for whom the concept of permanent population does not make sense (e.g. organizations) are not eligible for the bonus.
[EDIT: changed "issuer" to "issuing authority".]