G'day, a tip -
if you're going to a premium above melt value, make sure that you get either -
a high-grade coin;
or a low mintage coin;
or both !
Common years in high grade are easy to find for only a little above melt.
Australian silver was 92.5% (sterling) from 1910 to 1945;
but only 50% from 1946 to 1964.
The 1966 50-cent was 80% silver.
All of the other 1966 and subsequent coins are CuNi.
I see a lot of Australian silver & bronze & some notes on Ebay-USA, mostly bearing 1940s dates. I suspect that these coins travelled to USA as pocket-change of returning soldiers, and as they pass on, these mementoes are being found by families, and then into the market place.
Peter in Oz