The next challenge will be to post your smallest coin -- everyone that has at least one coin should be able to participate.
The challenge coin:
1/10 fanam (or bele), supposedly from India, but probably a modern fantasy or forgery:

This photo was taken with the coin lying on a stage micrometer. The coin appears to be about 1.90 by 1.93 mm in diameter, although this photo was taken with a non-telecentric lens, so the coin might be slightly smaller.
The following two photos show the obverse and reverse. These are is the only whole-coin photos I've ever taken with a microscope objective (so far).


Pointage:
One point for each whole millimeter in diameter. If the coin is not perfectly round (or not round at all), the largest diameter (or longest dimension) will be used. Fractional millimeters are rounded up to the nearest whole millimeter. The challenge coin is 1.90 by 1.93 mm, so 1.93 mm is used and gets rounded up to 2 mm, giving 2 points.
There is no special bonus for an exact match.
The participation bonus (for entries with no coin) will be a very generous 1000 points, corresponding to 1-meter diameter coin.
Other rules:
1) The coin with the fewest points wins. For point-based ties, the earliest post wins (not the coin with the smallest fractional millimeter size). If there are no valid entries, the first participation post wins.
2) All coin-like objects are OK -- examples: tokens, fantasies, reproductions, miniature novelty coins, unusual coins (in Krause), counterfeits/forgeries, etc.
3) Not allowed are small images of coins on currency, stamps, etc. or small coins forming part of the design on a larger coin (the size of the larger coin would count in this case). Also not allowed are individual gold dust particles, and the like.
4) The weight or thickness of the coin does not matter, only the diameter or other length/width measurement. (I suppose if you have a strange coin that is thicker than its diameter, the thickness would be the maximum dimension, so that would count in this unusual case.)
5) Please include the diameter or other maximum size with your post. If I can't figure out the size (especially likely with novelty items or tokens, etc.), only the 1000 participation points can be awarded.
6) I forgot to add -- The cutoff for entries is April 19, 10AM, forum time.