Fifty-six men, including John Hancock, put their John Hancocks on the Declaration of Independence in 1776. Collectively they are known as The Signers. In 1833, William Buell Sprague, who was not born until nearly 20 years after the Declaration, invented a new hobby: collecting the signatures of all 56 signers. There are two things that need to be said about this.
One is that inventing a hobby for yourself is an admirable achievement. But inventing a hobby for other people to follow...I don't know. It seems like an odd and slightly sketchy act, nearly anti-social. I say this on a hunch and practically no evidence, so I could be wrong; I welcome your counterexamples.
The second is that by defining the set to be collected so precisely, Sprague set in motion a long-term rise in the price in the autographs of all the signers. Some signatures were relatively easy to find, some were less common. But the scarcest of all is that of Georgia delegate Button Gwinnett.
Why? Because Gwinnett, during his 41 years of life before the Signing, for whatever reason, happens not to have put his signature on many pieces of parchment or paper that survived. Nor could he do so afterward, as he was fatally wounded in a duel in 1777. Unlike signer Ben Franklin, who lived twice as long and seems to have spent nearly every waking minute writing letters, Signer Gwinnett didn't sign much of anything else.
That made Button Gwinnett's signature the Babe Ruth rookie card of the Signer list, the rarest and hardest to find, even if you are willing to spend a fortune. The latest Button sig changed hands for over $750,000.
Every collection of any kind that is based on a list will include one Button, one piece more rare than the others. And if very many people are clutching the same scavenger hunt list, it's just the law of supply and demand. The rare piece soars in price, because everybody's got to have it.
In book collecting, the Button is the first edition of the first book of a very famous author before he got famous, so published in a small press run. In comic books, it's Spiderman #1, because Marvel was a fringey company and because Spidey was such a jerk. And if it is your heart's desire to own one license plate from every state, your Button is Hawaii. Nobody drives here from Hawaii.