Numismatic Feature - Bi-Metallic Coins and Medals

Bi-Metallic Coins and Medals

Bi-metallic coins are produced from two separate components of different materials/alloys, usually one white and the other yellow or gold coloured. The components comprise an outer ring (or annulus) and an inner disc (or core).

The outer ring is produced in a single blanking operation with the inner disc being blanked conventionally and then groove rimmed. The blanks are then prepared for coining, where the two components are fed independently into a specially modified coining press which brings the components together to be struck simultaneously to form the finished coin.

The designs featured on the coin are modelled to very precise specifications in relation to the ratio of the separate components. The specifications for coins are very exacting and strict controls on quality are applied not only after striking but throughout the course of production.

Source:
Certificate accompanying the 1994 New Zealand Proof Set - Reserve Bank of New Zealand, 1994.

The following Australasian Bi-Metallic coins have been issued:

1994 New Zealand 50c - Al-Bronze/Copper-Nickel; Al-Bronze/Silver and White/Yellow Gold;
1994 Australian $5 - Vote for Women;
1996 Australian $5 - Bradman;
1997 Australian $5 - Bradman and
1998 Australian $5 - Royal Flying Doctor Service;