The 1942-S Sixpence was struck at the San Francisco Mint with a mintage of 4,000,000. In the same year a further 8,968,000 pieces were struck at the Melbourne Mint and another 12,000,000 at the Denver Mint. The San Francisco variety can be differentiated from the others by a small 'S' mint-mark located above the date on the reverse. The variety is quite affordable even into mint-state where MS64 pieces can still be acquired for very reasonable prices. As with most years in the series the scarcity and prices grow rapidly beyond MS64.
The extremely large mintage of sixpence in 1942 was a response against a major shortage of both silver and copper coinage. One of the key reasons for this shortage was the mass arrival of United States soldiers into Australia from the Middle East theatre. These troops, along with a general increase in public spending, created an unprecedented demand for coins. The Melbourne and Perth Mint simply could not make supply match demand so a deal was struck with the United States. Under President Roosevelt's Lend-Lease Policy the United States agreed to provide Australia with a substantial quantity of silver coins. Australia guaranteed to then return an equal amount of silver after the war.
President Theodore Roosevelt had created the extensive Lend-Lease Policy in 1941 as a way to assist allied forces during the Second World War. The program allowed the United States to provide war materials including but not limited to ammunition, aeroplanes, and food that could then be paid for "...in kind or property, or any other direct or indirect benefit which the President deems satisfactory." The program proved essential to the allied war effort with the total value of the aid reaching $49,100,000,000. (Encyclopaedia Britannica, 2017)