Error Reverse: 2 horizontal bars behind Emu’s head
Incorporated in the original reverse design are 2 horizontal bars behind the emu’s head. The area of the reverse die behind the emu's head was rather weak (as evidenced by the existence of the "double bar" variety), and as a result that hub was retired and replaced with a modified one.


The 50 cent coin was first introduced with decimalisation on 14 February 1966. This original design featured the Commonwealth Coat of Arms struck in 80 per cent silver. Silver prices rose above the face value of the coin in 1967 and striking of the coin was suspended in March 1968.
Arms of the Commonwealth of Australia, based on those authorised by Royal Warrant 19 September 1912 - composed of a shield divided into six parts, each containing a representation of the badge of a State. The shield is supported by a kangaroo and an emu. The shield sits on the denomination numerals, 50 above the shield is the Federation star. The entire design is set above a field of stylized wattle leaves.
Elizabeth II (Elizabeth Alexandra Mary 1926 – 2022) was Queen of the United Kingdom and other Commonwealth realms from 
6 February 1952 until her death in 2022. She was queen regnant of 32 sovereign states during her lifetime and was head of state of 15 realms at the time of her death. Her reign of 70 years and 214 days was the longest of any British monarch and the longest verified reign of any female head of state in history.
OBVERSE: 2nd portrait of Queen Elizabeth II facing right wearing the Girls of Great Britain and Ireland Tiara
Lettering: ELIZABETH II AUSTRALIA 1966
Engraver: Arnold Machin
REVERSE: Australian coat of arms with large numerical denomination below
Lettering: 50 SD
Engraver: Stuart Devlin 
EDGE: Reeded 
Designer : Arnold Machin (1911–1999), was a British artist, sculptor, and coin and postage stamp designer.
Designer : "SD" -  Stuart Leslie Devlin (1931–2018), was an Australian artist and metalworker who specialized in gold and silver.
Mint: Royal Australian Mint, Canberra, Australia
Mintage in 1966          36,252,000
Country                    Australia 
Queen                              Elizabeth II (1952-2022)
Type                              Standard circulation coin
Year                              1966
Value                        50 Cents
Currency                  Dollar (since 1966)
Composition            Silver (.800)
Weight                      13.29 g
Diameter                  31.65 mm
Thickness                   2.5 mm
Shape                          Round
Orientation               Medal alignment ↑↑
References               KM# 67