All pre-1920 British Sixpences were made from sterling silver (92.5% silver content).
You could try eBay or a local coin dealer.
The last year British sixpences, shillings, florins, and half crowns were made with silver was 1946.
All British 1935 Sixpences were minted at the Royal Mint London. There are no "D" Sixpences.
I don't believe that any commonwealth nation ever struck a sixpence in copper and not in 1943. There were some sixpences struck in copper-nickel, but I'm not sure which ones were in 1943, British and Australian sixpences were struck in silver in 1943.
Fijian Sixpences, Shillings and Florins minted from 1934 to 1941 had a silver content of 50%. Fijian Sixpences, Shillings and Florins minted from 1942 to 1943 had a silver content of 90%. This is an unusual trend, moreso during the war years when most countries were moving away from precious metals in their currencies. Fijian general circulation "silver" coins minted from 1953 onwards have no silver at all and were made from a copper-nickel alloy.
The Royal Mint produced 6,382,793 British Sixpences.
1552 = 2 x 761
1552
With the possible exception of traders tokens (with the traders business name on them), there were no "Australian" Sixpences minted prior to 1910. The only Sixpences circulating in Australia prior to 1910 were British Sixpences.
There USED to be 40 sixpences in a pound. 2 sixpences = 1 shilling. 20 shillings = 1 pound
All British predecimal "silver" coins from 1947 onwards are made from a copper-nickel alloy consisting of 75% copper and 25% nickel.