Only three notable changes occurred in this series:
Reverse A was replaced by Reverse B in 1943 (a very small adjustment to the border teeth).
The final debasement to cupro-nickel took place in 1947, ending silver issues.
In 1949, following Indian independence, the royal cypher was changed. The earlier
GRI (Georgius Rex Imperator) became G VI R (Georgius VI Rex).
Unlike most denominations, which only needed word spacing adjusted, the sixpence
required a complete cypher modification.
The only date generally considered a "key" is 1952. While these are very common in VF,
they are much harder to find in true mint state.