It has been so long since we set things up I will have to do a bit of double checking with TKO. More than likely its a combination of things, including time here in the castle or perhaps the amount of gold and silver you send to the administrators. I will check into it before you start sending your collection my way! 
I vaguely remember one had to have started under bobby and susan and be moved to a corner as unworthy and then when the chief knight was banned ; moved with him into exile on yahoo . Then one had to find this castle and reapply for the same knight number.
The one aussie coin had to be sent to Merlin for inspection together with 11 others
half silver and half gold ........ If they were found worthy one was accepted as a master distributor . It helps to have a low knight number .

Since nobody can recreate this journey ( booby and/or sussan would throw a fit and we don't want to kill somebody unintentionaly do we ? ) we may have to apply a formula like twoshadows suggests .