1943 San Francisco mint Shilling
While probably the most common date in the series in lower grades, the case is perhaps very different in mint state. With the highest mintage in the series, there is no doubt that sorting through a sack of circulated shillings will yield numerous examples of this date, however the case in mint state is often very different. The reason being is that mint state quantities are generally defined by the notable hoards that turn up. For example, the Vienna hoard brought about many 1944 San Francisco mint shillings contributing to their availability, a few mint rolls of 1941 shillings have turned up also, but just what has turned up of the 1943 San Francicso mint shilling?
At the time of writing, the PCGS population chart shows only 6 1943 San Francicso mint shillings, that's the lowest of George VI and the 4th lowest of the shilling series as a whole, after the 1915-H , the 1913 and the 1921 Star. Now of course nobody is going to bother sending circulated examples of this date to PCGS as they're almost as common as sand so it would be more realistic to compare the number of mint state examples that they've handled, which would put it at equal lowest in the George VI series with the 1942, another potentially scarce date.
The 1941 and 1944-S on the other hand have the highest populations of the series with 30 and 37 respectively demonstrating the influence that notable hoards have on the survival rate in mint state.
I have only encountered 1 !bank roll of the 1943 San Francicso shillings, offering 40 mint state examples which would probably range from MS62 to MS64 if slabbed and so while the 1943 San Francicso mint Shilling probably isn't scarce than the 1940, it is certainly an underrated date of the series and one should not underestimate how difficult they are to acquire, especially if sought in the higher mint state grades.
You can view this article along with valuations and much more at the Blue Sheet: 1943-S Shilling