LONDON (Reuters) - Those lucky spectators streaming into the Olympic Park for Friday's opening ceremony would be well advised to keep their ticket stubs, and any other ephemera related to the occasion, if only for their great-granchildren's sake.
If they have not already binned it, they might also want to hang on to the stiff postal envelope that the coveted tickets arrived in.
In the world of the Olympic memorabilia collector everything associated with the Games is of potential interest, even if it could be many decades before anyone can turn the trash into cash.
That alchemy, the act of trying to identify the base matter that might one day be transformed into saleroom gold or family heirloom, is all part of the fun.
As the late IOC president Juan Antonio Samaranch, a noted philatelist, once declared: "Collecting is the sport of the spectator".
Medals will always be the most obviously sought after items, because each one carries an individual story, has an intrinsic value and there are not many of them handed out.
Relay torches are also good sellers and pins have been traded for decades now.
"Once you get beyond the medals though, it becomes much trickier to predict what might become valuable or collectable in the future," Lionel Willis, a memorabilia expert with London auctioneers Bonhams, told Reuters.
"From this Games, we are generating an enormous amount of material of all sorts of ephemera, both printed material, bits of kit and souvenirs and all this sort of stuff - none of which is particularly special right now.
"But in 100 years' time it may well be that just a scarf from an Olympic 'meeter and greeter' in the Park might be valuable, because there's only one left."
To prove his point, a cotton swimsuit and cap worn by British backstroke swimmer Eric Seward at the 1908 Games sold for 3,250 pounds ($5,000)at a Bonhams auction on Wednesday, despite the swimmer being eliminated in the heats.
A score keeper's badge, complete with box, from the same Games sold for 1,625 pounds.
Only 60,000 people will attend the opening ceremony, after more than a million had sought tickets. That already puts a rarity value on the item.
Even rarer will be the tickets for the most expensive elite seats that cost 2,012 pounds or the cheapest offered at 20.12.
Some eagle-eyed philatelists have already spotted that the envelopes the tickets were sent in carried a special printed label declaring 'Postage Paid GB HQ2012' -- sent from Games headquarters.
Keeping the used tickets and envelope together for posterity might one day make all the difference. It just depends on how many others do likewise and how much material survives the ravages of time.
"It's not an easy business to predict, I can assure you of that," said Willis.
Games organizers LOCOG have set up their own auction website (www.london2012.com/auction) to sell off memorabilia and offset some of the huge costs of staging the Olympics [ID:nL3E8HK5HS].
Items will include a baton from the men's 4x100m relay and tennis balls used in the tournament at Wimbledon. A torch carried by former England captain David Beckham when the Olympic flame arrived in England from Greece in May was put up for auction already.
The record for Olympic memorabilia was set in April when a tiny silver cup from the first 1896 Olympic marathon won by Greece's Spyros Louis sold for 541,250 pounds ($837,500) at Christie's [ID:nL3E8FI5JC].
An exhibition at the British Library, just down the road from the St Pancras International Station that tens of thousands of fans will pass through in the coming days, puts the focus on more ordinary and obtainable items.
"Olympex 2012 - Collecting the Olympic Games" is a free display put on by the Library and International Olympic Committee and runs until Sept 9.
Most of the material comes from individual collectors rather than museums and much of it has been on auction site eBay over the last 10 years.
One case contains the finishing 'tape' broken by the 1908 marathon runner Dorando Pietri at the first London Games before the dazed Italian was controversially disqualified for being helped across the line by officials.
A simple length of worsted, broken from a large skein of wool kept on a pole at the finish line, it might easily have been discarded. Instead, the chief judge of the marathon put it in his pocket and, later, in an envelope noting the details.
In the collecting game, provenance is everything -- something demonstrated recently when a piece of toast from the breakfast tray of Prince Charles on the morning of his marriage to the late Princess Diana sold for $361.
"It is very simple, but priceless," Bob Wilcock, vice-chairman of the Society of Olympic Collectors, told Reuters of a plain piece of wool that looks like something left over from Granny's knitting.
"It has a very important historical story attached to it."
There are programs, posters, postcards and even a piece of 'fan mail' -- a message to admirers from 1911 saying that "If you have the will, you can succeed in everything. Dorando Pietri".
There are sheets of postage stamps and an early example of 'ambush marketing', with a tire brand printed as advertising along the 1908 marathon route where no such hoarding had existed in reality.
Another photograph shows 61-year-old British runner Thomas Jack, who led the 1908 marathon briefly before stopping at the Crooked Billet pub where he "had recourse to refreshment" and retired soon after.
"Talk about crowds here," writes an unknown hand on a postcard sent from Windsor on Marathon day 1908. "It's just like the picture here today," says another from Henley where the rowing took place.
The messages are not so different from modern social media, the daily outpourings on Twitter and Facebook from fans and athletes alike. Like the postcards of our ancestors, they too could conceivably have a value one day.
"What happens to all the Tweets?," asked Wilcock. "Some of them are going to be very interesting. They are all going to go unless you have got something physical, tangible.
"You've either got to upload all your messages on to your computer and your images and make sure you keep them. Or you've got to get paper."
Most of the messages sent in the past would have ended up in the waste paper basket, their contents deemed insignificant, but a small amount survived and are now of real interest. The digital era may be no different.
"If you sent a Tweet to an athlete and you got a reply from that athlete, saying 'Thank you' or whatever, then you keep that and it has some value," said Wilcock. "It is the changing world of collecting."
($1 = 0.6463 British pounds)
Editing by Greg Stutchbury