ELIZABETH II 1952-PRESENT (Minted 1953-1967 & 1970)*Obverse by Mary Gillick, Reverse by Edgar Fuller and Cecil ThomasThe first issue of 1953 is a one type only issue, being the only year that BRITT OMN (of all the British possessions) was included in the obverse legend, it was omitted the following year when the dies were recut.
The striking on the 1953 issues is somewhat poor, as the whole issue was weak struck, (this goes for all the other denominations too), pictured below is an UNC example (believe it or not!)...

The coins minted in the subsequent years were of a higher standard than those of 1953, and notice the lack of the BRITT OMN...

The series ended with the coins dated 1967, the dies were used to strike coins well into 1968.
With Britain set to go decimal in 1971, there was no room for the sixpence thus mintage ceased in 1968. The decimal penny being worth 2.4 old pennies meant that the sixpence would become revalued at 2.5 new pence, it survived beyond 1971 as it was possible to get correct change for this particular denomination, unlike the threepence for example which became worth 1.25 new pence, the public would only have been able to spend them in twos otherwise it would be impossible to get correct change, same scenario with the penny. Thus the latter two were demonetised whilst the sixpence survived.
In 1970 just before decimalisation there was a special mintage of proofs in considerable numbers to mark the passing of pre-decimal currency into the history books...
below is one of those last sixpences...

By the late 1970s however, the government was discouraging the use of sixpences as they considered a 2 1/2p coin to be somewhat of an anomally, by this stage of course even the decimal halfpenny was considered pretty pointless. The sixpence was finally demonetised during the summer of 1980.