Matthey Garrett Pty Ltd manufactured medals during (at least) the late 1960s and 1970s. Matthey Garrett Pty Ltd (Sydney Refiners) were also melters and assayers of good delivery gold bars.
Their issues included 1966 Sir Winston Churchill and Robert Menzies medals, a 1970 18ct gold replicas of the First State and First Commonwealth, 1st Queensland and Victorian postage stamps, a 1970 Captain Cook 200th anniversary gold medallion set with a Matthey Garrett certificate, 1970 medals for the Royal visit and a 1973 18ct gold medallion pair in a case to commemorate the Royal Visit and Opening of the Sydney Opera House. Matthey Garrett's gold and silver bars included a one ounce pure silver bar for the Western Australian sesquicentenary in 1979.
London Bullion Market Association website http://www.lbma.org.uk/good_delivery_gold.html