Proof that buying one of Australia's rarest coins will cost a pretty penny

Proof that not everything should be taken at face value, with a rare Australian penny on display in Melbourne valued at $1.25 million.

The 1930 proof penny is one of six struck, but never circulated, in Australia's pre-decimal currency era.

Its value has soared over the years due to its extreme rarity.

Three of the six 1930 proof pennies are privately owned, with one in Melbourne and two in Sydney. The other three are located in the British Museum, the Museum of Victoria and the Art Gallery of South Australia.

The coin was displayed under tight security alongside other rare coins and banknotes worth millions of dollars.

The exhibition continues tomorrow at Bayview on the Park in Albert Park.