2004 20 Cent Varieties
In 2004 the Royal Australian Mint began transitioning to computerised engraving of dies. For most denominations the new technology was used from 2005 onwards but the 2004 20c was produced using both old and new technologies (p128, McDonald, Pocket Guide to Australian Coins and Banknotes, 2017).
The old-style coins have a larger portrait with pointed top A's in the legend (so-called big head coins) and the new-style coins have a smaller portrait with flat top A's in the legend (so-called small head coins). Most circulating coins are small head coins with large head coins making up about 1.2% of the total mintage. Most or all mint and baby sets are large head coins and proof sets contain both large head and small head coins though the proportions are unknown.