I don't understand why you would need a scale that goes to 0.0001 grams. The coins are going to vary in the >+/-0.01 gram range anyway.
Learning to ID and collecting all 7 varieties out of circulation is fun, but only the 8th one is really worth anything and I don't think a third one will ever be found. It's been almost 5 years since the second one and people have been beating their brains out looking for another one.