What could be more personal than a passport? Most of have one, keeping them safely tucked away in a drawer at home (or it was last time we checked), and when we do travel we keep it close to us.
But have you ever considered a passport more than just a means of getting past surly airport staff? When you think about it, they are the repositories of the journeys we take - and can offer a unique window into the past.
The possibilities for passport collectors are endless - from those that carry the names of nations that no longer exist, to those that bear the traces of the most unforgettable moments in human history.
Celebrity passports are a particularly fascinating area of this branch of collecting, offering not only a personal item but also signatures and, more often than not, a less than flattering photograph.
This unique aspect is reflected in the strong values of passports from some of history's most iconic figures, many of who left few signatures behind. They can achieve major sums at auction.
A passport issued to Steve McQueen in 1970, for instance, which he used while filming the 1971 film Le Mans in France, made $37,500 at Profiles in History in 2012. It includes two striking signatures along with destination stamps from Jamaica, Madrid and Casablanca.
Going back further in time, the modernist writer James Joyce's British wartime passport achieved an impressive ?�61,250 ($98,000) at Sotheby's London in 2011.
Issued to the writer in 1915 by the British consulate in Zurich, it documents his movements during the time he was writing Ulysses - his most enduring masterpiece.
You can view rare and collectible passports at picollecta.com.
Currently the most valuable passport in the world is that of Norma Jeane DiMaggio, who is perhaps better known as Marilyn Monroe.
Issued in 1954, the year she married baseball star DiMaggio, it features four signatures, two using her stage name and two employing her married name.
The passport features stamps from Japan, where the couple honeymooned, and Korea - where she entertained US troops celebrating the end of the war.
It sold for $115,000 at Hunt Auctions in 2006.
More information on collecting passports can also be found at passport-collector.com, which offers a wealth of intriguing resources on the subject.
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