In 1999 to celebrate one hundred years of operation, the Perth Mint produced P100 Mint Marked proof and uncirculated bi-metal sovereigns. The uncirculated coin came in a dark green "crocodile skin like" case had a proposed mintage of 50,000, but from figures released in 2013 only 977 were ever issued. That's a pretty big difference. Can anybody tell me what happens to the unused cases, if there were any. Were they used on a later issue, destroyed, or just never delivered?