Hey, I tried emailing via geocaching.com but no answer so posting a note here in hope of a response.
I've retrieved your Australian Flag Micro Geocoin from Mannerheiminpuisto where it was dropped but am having troubles dealing with it. The code listed on it is the public reference that everyone can see on geocaching.com. Usually a TB has a different code listed on it that only people holding the TB can see so you can only log an action when you've actually seen the TB.
Only you can see this code online, it's on the righthandside of the Trackable's homepage under the Trackable Options section it's the "Tracking Number". This is the number that should be on your coin. Without it anyone trying to log an action on the coin gets the following error:
"The number you entered is the public reference number for this Trackable. Please enter the private tracking number located on the Trackable itself in order to post a log. "
If you can send me the tracking number I'll try and dismantle the coin and insert it for you. No idea how kuu_mar picked up the coin before me.