You never know what will turn up when you’re browsing at a flea market, searching through your attic or basement, going through an old barn or even looking through a boarded-up projection booth. Here are eight of the most surprising historical objects that people have ever found by accident.

1. 1931 Frankenstein Poster

Frankenstein, poster, Boris Karloff, Colin Clive, 1931. (Photo by LMPC via Getty Images)
LMPC via Getty Images
Poster from the 1931 Frankenstein movie, starring Boris Karloff.

Steve Wilkin was looking through a boarded-up projection booth in the Long Island theater where he worked as a teen in the early 1970s when he discovered a six-foot-tall poster for the 1931 movie Frankenstein

The film, based on Mary Shelley’s 1818 book of the same name, catapulted Boris Karloff to stardom, spawned several sequels and helped launch the Universal Classic Monsters movie series.

In 2015, the poster sold for $358,500 through Heritage Auctions, an auction house in Dallas, Texas.

2. Original Copy of the Declaration Of Independence

Declaration of Independence Copy Up for Sale371385 03: One of only 25 known surviving copies of the Declaration of Independence which were printed July 4, 1776 sits on display at Sotheby''s June 22, 2000 in New York City. The historic document will be sold in a one-day sale June 29th, 2000. It is estimated to be worth between $4,000,000 and $6,000,000. (Photo by Chris Hondros/Newsmakers)
Chris Hondros/Newsmakers
One of only 25 known surviving copies of the first printing of the Declaration of Independence, which sold n 2000 for $8.1 million.

In 1989, a man got more than he bargained for at a flea market in Adamstown, Pennsylvania when he bought a framed painting for $4. He found a document folded up behind the painting, which experts later identified as a rare first printing of the Declaration of Independence. The document is one of about 200 copies the printer John Dunlap made after the declaration’s ratification on July 4, 1776. The ink was still wet on this copy when it was printed, an auction expert told The New York Times, evidenced by the first line of the Declaration’s text appearing in reverse at the bottom of the page.

In 2000, TV producer Norman Lear bought the copy discovered at the flea market for a record $8.14 million through Sotheby’s, a global auction house.

3. Bronze Age Sword

While fishing in Northern Ireland’s Arney River in 1965, Ambrose Owens discovered an unusual object. He left it in an old barn on his family farm in County Fermanagh, where it sat for more than 50 years until his brother Maurice passed it along to archaeological experts. Maurice was shocked to learn that the object was a Bronze Age sword dating back some 2,600 years.

In 2016, BBC News reported that Enniskillen Castle Museums in County Fermanagh planned to take over maintenance of the sword.

4. Wallace Hartley’s Violin From the Titanic

Titanic Violin Goes On Display To The PublicDEVIZES, ENGLAND - APRIL 15: Auctioneer Alan Aldridge of auctioneers Henry Aldridge & son holds the violin of Wallace Hartley, the instrument he played as the band leader of the Titanic, on the 101st anniversary of the sinking of the ship, April 15, 2013 in Devizes, England. The auction house, which specializes in Titanic memorabilia and is having an associated sale on Saturday, spent seven years proving the violin was genuine and belonged to Wallace Hartley, who with his orchestra, famously played on as the ship sank in April 1912, and were among the 1,500 who died. Long thought to have been either lost at sea or stolen, it is being described, as far as Titanic memorabilia goes, as one the most important pieces that has ever come up for sale. Thought to be worth a six-figure sum, it is the property of an unidentified individual in Lancashire and will be displayed to the public all week, but Aldridge's have not yet confirmed when it is likely to go on sale. (Photo by Matt Cardy/Getty Images)
Matt Cardy/Getty Images
Auctioneer Alan Aldridge of auctioneers Henry Aldridge & son holds the violin of Wallace Hartley, the instrument he played as the band leader of the Titanic.

In 2006, a man in England found an old violin in his attic that turned out to be the one Titanic bandleader Wallace Hartley played as the ship sank in 1912. Shortly after the disaster, recovery workers found the violin in its case strapped to Hartley’s body at the site of the wreck. (Like many of the people who died that night, he was wearing a life preserver that kept his corpse floating in the water.)

Recovery workers sent his body and violin to his fiancé, Maria Robinson, in England. After her death, it passed through several other hands before landing with the mother of the man who found the violin in his attic.

In 2013, the violin sold for around $1.7 million through Henry Aldridge & Son Ltd, an auction house in Devizes, England, a record for a Titanic artifact. It has since gone on display at the Titanic Museum Attractions in Branson, Missouri and Pigeon Forge, Tennessee.

5. Lost Imperial Fabergé Egg

The Third Fabergé Imperial Easter Egg, displayed at Court Jewelers Wartski on April 16, 2014 in London, England. This rare Imperial treasure, made for the Russian royal family in 1887, was seized by the Bolsheviks after the Russian revolution. After being sold at auction in New York in 1964 as a 'Gold watch in egg form case' for $2,450, its ownership chain became unknown. A buyer in the U.S. Midwest purchased it in 2004 for possible scrap metal value.
Peter Macdiarmid/Getty Images
The Third Fabergé Imperial Easter Egg, displayed at Court Jewelers Wartski on April 16, 2014 in London, England. This rare Imperial treasure, made for the Russian royal family in 1887, was seized by the Bolsheviks after the Russian revolution. After being sold at auction in New York in 1964 as a 'Gold watch in egg form case' for $2,450, its ownership chain became unknown. A buyer in the U.S. Midwest purchased it in 2004 for possible scrap metal value.

In 2004, a scrap metal dealer found a gold, jewel-encrusted egg at a flea market in the U.S. Midwest. He bought the egg, which opened up into a clock, for $13,302, hoping to melt it down and resell it for more. Upon researching it, he began to suspect that it was one of the lost eggs made by the House of Fabergé for the Russian royal family—objects revered as pinnacles of design and craftsmanship and valued in the tens of millions of dollars. Experts confirmed that his flea market find was indeed the Third Imperial Fabergé Egg that Russian Tsar Alexander III gave to his wife, Maria Fyodorovna, for Easter in 1887.

In 2014, the egg was sold privately through a London auctioneer for an undisclosed sum.

6. Rare 1961 Ferrari

A 1961 Ferrari 250GT SWB California Spyder, long considered lost, was found in a treasure trove of 60 broken-down classic cars abandoned for decades by the Baillon family in a French field.
John van Hasselt/Corbis via Getty Images
A 1961 Ferrari 250GT SWB California Spyder, long considered lost, was found in a treasure trove of 60 broken-down classic cars abandoned for decades by the Baillon family in a French field.

The 60 classic cars—most of which started out as unique, luxurious, handcrafted beauties—had languished in the elements for decades. Some had been overtaken by vines and weeds, and most were turning into rustbuckets. Discovered on a farm in western France, they were originally owned by French entrepreneur and car enthusiast Roger Baillon, who began collecting them in the 1950s, and whose plan for an open-air car museum was foiled in the 1970s by his failing finances. When Baillon's grandchildren inherited the farm, they discovered the decaying trove.

Among the cars in better condition was a rare 1961 Ferrari 250 GT SWB California Spyder, one of only about a dozen of this particular model made by the renowned sports car maker. It had once belonged to French actor Alain Delon, boosting its provenance.

In 2015, the car sold for $18.5 million through Artcurial, an auction house in Paris.

7. More Than 700 Vintage Baseball Cards

While cleaning out his aunt’s attic in Defiance, Ohio, Karl Kissner was surprised to discover more than 700 baseball cards dating from around 1910. The nearly pristine cards, part of an extremely rare series that had originally been given out with candy, featured Hall of Famers like Cy Young, Honus Wagner and Connie Mack.

In 2012, Kissner’s family sold the first batch of 37 cards for $566,132 through Heritage Auctions.

8. The First Superman and Batman Comics—Plus 343 Others

Action Comics No. 1 Introducing SupermanCover illustration of the comic book Action Comics No. 1 featuring the first appearance of the character Superman (here lifting a car) June 1938. (Photo by Hulton Archive/Getty Images)
Getty Images
Cover illustration of the comic book Action Comics No. 1 featuring the first appearance of the character Superman (here lifting a car) June 1938.

Michael Rorrer was cleaning out his great-aunt’s home in Virginia when he discovered 345 comic books stacked in the basement closet. He later learned that his great-uncle had compiled the collection, which included the first appearances of Superman and Batman, as well as the first issue in the Batman series.

In 2012, a large portion of these comics sold for $3.5 million through Heritage Auctions. The top seller was a 1939 copy of Detective Comics No. 27, the first comic in which Batman appeared, which went for about $523,000. A 1938 issue of Action Comics No. 1, the first comic in which Superman appeared, sold for roughly $299,000; and a 1940 issue of Batman No. 1 sold for about $275,000.