The Tuvaluan Dollar is the currency of Tuvalu - a small nation in the Pacific Ocean. Tuvalu has never had banknotes of its own, and has been issuing coins since 1976; these circulate together with coins of the Australian Dollar, which is also legal tender in the country, and to which the Tuvaluan Dollar is pegged.
The Australian Perth Mint issues a large variety of non-circulating legal tender coins under the authority of Tuvalu. Some of these are in the half ounce silver format (abbreviated as 1/2 oz). Strictly speaking, they are not bullion as they are priced at a premium and are targeted at collectors who appreciate them for their artistic merit and collectable value and not just for their precious metal content.
The overall weight of the coins (including the 0.01% of other metals) is slightly over one half of a troy ounce, so that they have exactly 0.500 ASW (Absolute Silver Weight).