Want to turn 30 cents into $500 or more in just three weeks? It's very simple: just stand by your post box and wait.
The catch is you will have to be very, very lucky - and have friends in Adelaide.
Australians will have noticed that in 2016 it now costs $1 to post a standard letter, up from 70 cents last year. But even Australia Post wasn't completely ready for the change, so on January 4 the Adelaide GPO cranked up an old printing machine and quietly produced an "emergency" run of 30 cent stamps to allow the public to make up the difference between the old rate and the new.
These six counter produced stamps (three depicting kangaroos, three koalas and all marked "Adelaide 2016") are plain looking, but very special.
They were produced in very small numbers at the Adelaide GPO. They were only sold at a few South Australian suburban post offices for three or four days, until the supply shortage was overcome with the regular 30 cent "Crocodile" design stamps printed in their millions in Melbourne.
On top of that, this is the first time since Federation that Australia's postal issuing authority has released emergency printed stamps. Members of Stampboards.com, the website for the stamp collecting community where the emergency printing was revealed on 18 January, believe that whatever supplies each post office had are now long gone.
So the hunt has begun in the wild for mint versions of the stamps, but also those used on letters. Across the global stamp collecting community, it is what you might term a frenzy.
When one set of all six stamps appeared on eBay last week, the price rapidly rose. With a combined face value of just $1.80, they soon vaulted over $200, then $400 before finally settling on an astounding $1,051.11 as two bidders fought it out to the end.
A letter with a 30 cent stamp next to a normal 70 cent stamp, sent to the Adelaide suburb of Salisbury Heights, is expected to easily exceed $500 by the time the online auction finishes this Sunday.
Any Australian could be a winner; an unknown quantity of the rare stamps were sold to people who simply wanted to use them to post a letter at the new $1 rate. And those letters have now arrived in Australian homes or are on their way.
A prominent Sydney stamp dealer, Glen Stephens, managed to source multiple sets of six of the unused stamps from an Adelaide collector, which he readily sold even as the price rapidly went up to $550.
One stamp collector fanatic managed to overcome not actually being on the planet to buy a set from Mr Stephens - he's the Russian cosmonaut presently circling the Earth commanding the International Space Station.
Another veteran stamp dealer, Rodney Perry, who specialises in complete letters (or "commercial covers" as they are known), said on Stampboards.com he believes this is where the real value will be, especially for any letters posted on or around the first possible date of January 6. He termed this issue "a modern rarity".
This is not the first time stamps have been printed in a rush to meet demand. The most celebrated case is the British Guiana 1 cent Magenta, locally produced in Georgetown in 1856 because the ship that was meant to bring stamps from Britain did not arrive.
Like the 30 cent Adelaide stamps of 2016, the key is that it was also an official product carrying the imprimatur of the local postmaster. That 1 cent stamp is the only one of its kind to survive and in 2014 was sold in Sothebys for a world record $US9.5 million.
An Australia Post spokesman said they were aware of the sudden interest in the 30 cent stamp, and while there have been recent requests for these to be reprinted, there is now no need and this will not occur.