A set of 20p coins has been printed without a date on them, making them very rare, and very valuable.
In fact, they're worth £50 each!
So do you own anything that's unusual or rare?
Maybe you've got a rare stamp, a first edition Harry Potter book or perhaps you've managed to get David Beckham's autograph.
Or have you got something that's special just for you - a memento of a holiday or something from when you were very young?
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"I've got an authentic Victorian coin which my Dad found when he was digging up the garden."
Sam, 8, London, England
"I have a Blue Peter badge, some rare Doctor Who cards and a David Beckham Academy football."
Megan, 13, London, England
"I have a copy of Harry Potter and the Deathly Hallows signed by JK Rowling."
Amelia, 13, London, England
"I have a Victorian 5p coin I found on the street."
Kelsey, 11, Blackburn, England
"I've kept my baby teeth in a little jar. I still have them!"
Agne, 10, London, England
"I have a letter from Jacqueline Wilson!"
Louisa, 10, London, England
"I also have a fossil which is around 440 years old. I got it in Bath when I went on holiday. You could not even tell it was that old!"
Rachel, 13, Manchester, England
"I have Quentin Blake's autograph. I received it when I was in Y4. I am moving into Y7 in September!"
Ben, 11, Durham, England
"I own lots of Dr Who items. I can't write all the stuff but my most weird item is the fake Dr Who money that was used for the 2006 Christmas episode, The Runaway Bride."
Sam, 12, Cambridgeshire, England
"I've got an AC/DC dollar bill from one of their concerts, apparently they are worth £100."
Tyla, 11, North Yorkshire, England
"I have a massive stamp collection of my dad's. It has more than 500 stamps in!!!"
Lilly, 14, London, England
"I found the 20p coin worth £50."
Anne-Marie, 13, London, England
"I have all of Disney's autographs and Daniel Agger's."
Sara, 14, Wales
"I own a first edition limited edition Harry Potter book and a letter from JK Rowling! The stamp on the letter is a rare Slytherin stamp!"
Rachell, 11, Aberdeen, Scotland
"I own headphones that look like bananas. :) they're awesome :)"
Alys, 13, Wrexham, Wales
"I have a strange looking cup which looks like a toilet, I got it from china!"
Thormajoo, 11, London, England
"I have Buzz Aldrin's autograph that I bought with my savings."
Emily, 11, Stockport, England
"I've got Dani Harmer, Andy Akinwolere and Raven's autographs."
Emily, 11, Glasgow, Scotland
"I own two genuine Roman coins."
Richard, 10, Kent, England
"I collect rubber ducks - they're cheap, cute, easy to find and are just great to keep on your shelf. I've got 16 of them!"
Ellie, 12, Kent, England
"I have got Britney Spears' autograph!"
Jazmine, 10, Ipswich, England
"I have a piece of paper that's got the king of Saudi Arabia's signature on it!"
Naseera, 13, Leicester, England
"I have Freema Agyeman's autograph, I had to write her a letter for it."
Colette, 15, Worcestershire, England
"I have the purple cast from when I broke my arm about four years ago!"
Hannah, 13, Shropshire, England
"I have lots of celebrity autographs and it's really amazing!!!"
Ivery, 13, Birmingham, England
"I have two coins from the Tudor times."
Genina, 11, Oxfordshire, England
"I own three unique things. A first addition of a Harry Potter book, a letter from Jacqueline Wilson and a Blue Peter badge."
Hannah, 10, Kingston, England
"I have a coin collection that my mum gave me when I was 10, and they are in a glass case and they date back to 1900! The 5p pieces are massive!"
Evie, 12, Lincoln, England
"I have a collection of glass animals."
Lulu, 12, London, England
"I have a photo of me and Sir Alan Sugar and a chocolate bar wrapper signed by Fernando Torres!!"
Toby, 12, Cheltenham, England
"I have three fake pound coins! I'm going to keep them rather than spend them, and apparently one in fifty pound coins in the UK are fake!"
Charlotte, 13, Dundee, Scotland
"I have an arm cast signed by an astronaut!"
Liz, 13, London, England
"I have David Beckham's autograph and Bobby Charlton's too. They are in a frame on my shelf."
Liz, 15, Hertfordshire, England
"I own a weird fossil that looks like an underwater shell, and it's really rocky."
Cowie, 12, Cornwall, England
"I have a coin from 1912."
Adam, 12, Telford, England
"I have lots of people's autographs and a lot of Charlton players' too."
Vicki, 12, Kent, England
"I have a stamp collection and Andy Murray's autograph."
Zainab, 14, Ealing, England
"I have loads of old coins, but the oldest dates back to Roman times!"
Natalie, 13, Buckinghamshire, England
"I have a picture made out of petals."
Megan, 11, UK
"I have an inflatable Spider Pig!"
Alice-Mae, 11, Suffolk, England
"I have the Saturdays' autographs and my dad's stamp collection which has a lot of stamps. And I have two letters from Queen Elizabeth!"
Alice, 11, Northampton, England
"I have a signed first edition of Harry Potter and the Philosophers' Stone and a 1911 one dollar bill."
Mac, 10, Stockton-on-Tess, England
"I have a Roman coin at home from the rein of Emperor Gallienus."
Oliver, 11, Hertfordshire, England
"My great nan died and left me a gold necklace, but I can only have it when I'm 18."
Olivia, 10, Bradford, England
"I own a fossil that I found on a beach in Ireland."
Sarah, 12, Leeds, England
"I have some real gold in a bottle. I found it on holiday in Jersey."
Florence, 7, Warwickshire, England
"I have a real shark's tooth! It's a lot smaller than you would think!"
Michelle, 12, Ireland
"I have a spoon that has a map on the round piece. I love it although my mum and dad thinks it's weird!"
Lucy, 9, Kent, England
"I have a bean lizard from my holiday in France but I don't know if it's very special. There was only one in the tub."
Ellen, 10, Manchester, England
"I have Alan Shearer's autograph."
Benny, 11, Kent, England
"I have a coin from the time that England won the World Cup but I don't know if it is very rare or unusual. I found it in the library."
Aimee, 12, Somerset, England
"I have a pet penguin."
James, 12, Isle of Man, England
"I own a 400 million-year-old fossil nautiloid shell and a coin from the last year of Queen Victoria's reign."
Rory, 11, Belfast, Northern Ireland
"I have some ration cards from the World War 2 that belonged to my Grandma."
Claire, 11, Lisburn, Northern Ireland
"I made a coin collection with more than 250 coins worth around £100."
Sasha, 12, Aberdeen, Scotland
"I have a Duff beer glass all away from Spain!"
Aaron, 13, Northern Ireland
"I have the piggy boxes from Natwest my sister passed down to me."
Beth, 12, Kent, England