Rare coins and stamps are now an established asset class.
Coins were nominated as the third-best-performing asset on a December 2013 Deutsche Bank list - increasing by 60 per cent in value since July 2007. Rare violins (133 per cent) and gold (91 per cent) were the two top performers.
Banknotes, it appears, are yet to be accepted in this blue-chip category.
Two Saturdays ago, several prime examples were included in the numismatic auction held by Roxbury's Auction House at the Hotel Grand Chancellor in Brisbane.
Roxbury's director Bob Innes said before the sale it was one of the highest quality and most diverse collections the auction house had ever put together.
''It will provide a good measure of where the market currently stands.''
The post-mortem is that pre-decimal coins are still in demand, but investors are cautious about rare banknotes.
Case in point was the highlight of the auction, a 1923 George V £1000 ($1661) specimen note. It comes with a fascinating provenance.
The Australian Commonwealth Treasury first introduced a £1000 note in 1914, primarily to assist in the transfer of large sums of money between banks.
In total, 88,585 of these were printed, but the Governor of the Commonwealth Bank, concerned about the risk of counterfeits, decided they should not be released for public circulation.
In 1922, it was decided to print some new notes (known as Type 2). A specimen was received in 1923, but by then bank usage was decreasing and it was decided not to proceed with the new design.
This makes the 1923 specimen note one of Australia's rarest. It was Star of the Show at the Numismatic Association of Australia's Coin Fair in 1994 and most recently sold for A$890,000 ($968,765) in 2008.
Last Saturday, it was listed with a very low estimate of A$250,000 and was passed in, failing to reach its much higher reserve price. So, what happened?
''The bubble has started to burst,'' Jacquie Innes, of Roxbury's, says.
Part of the problem is the recent demise of two of the more prolific dealers in rare banknotes, which will see a large number of portfolios released for sale throughout this year.
''The market is just not sustainable.''
Another factor is the complexity of SMSF regulations, which Innes says has scared off many investors. Coins are seen as less risky. This is not to say shrewd collectors aren't still buying banknotes.
On Saturday, a 1923 large K-Prefix £1 note, described as very rare, sold for A$40,200, including buyer's premium (IBP).
Its estimate had been A$35,000. A 1913 £10 note, Type 3 specimen - ''unique in private hands'' - sold for A$62,00 IBP.
In comparison, one of two 1930 pennies listed sold for A$12,600 IBP. These coins, once considered the Holy Grail, are now relatively common at auction. The second penny did not sell on the day.
Nor did a Sydney Mint proof half sovereign, estimated value $65,000. But, in general, coins sold better than paper money. Lot 1372, a Colonial Bank of Australia £5 note sold for A$520 IBP (estimate A$1250), and Lot 1373, a Federal Bank of Australia £50 note, went for A$600 IBP (estimate A$1500). These might prove to be bargains, but who knows?
Modern banknotes are also collectable. A 1988 Bicentennial A$10 sold for A$5000. And among the desirable error notes, an uncirculated 1992 A$5 sold for A$1450. Its error is rather obvious. Someone forgot to print the colour black.
- Sydney Morning Herald