They include Preston van driver Harry Hopkins who found his rare 20p piece in his pocket and has since placed the coin for sale
on the eBay auction website.
The 67-year-old joins other Preston traders including one who sold a
copy of the undated 20p piece for £301 following 31 bids on the site while another fetched £225 after eight bids.
The finds come amid advice from one Lancashirebased coin collecting expert to sell the 20p pieces as quickly as possible before they go down in value.
Mr Hopkins, of Salwick Place, Ashton, said he hopes to sell his coin
online after a trader sold one for £7,100 on the website.
He said: "I found it last Monday in my pocket and do not have a clue where it came from. I had a look at it and was very pleased as I heard they could be worth £50.
"I later spoke to a friend who said they were going for as much as £5,500 and thought I will keep hold of this. I felt very excited."
It is thought up to 200,000 undated 20p pieces have been released into
circulation after the Royal Mint accidentally printed a batch without a
date, the first time in more than 300 years that undated coins have been
released.
The error occurred after the old design was replaced by a new edition,
switching the date from the tail to the head side in 2008.
The London Mint Office is also offering to pay £50 each to anyone who sends them undated 20p coins, but there have been reports of coins being priced as high as £20,000 online with eBay confirming
one sold for £7,100.
Jeremy McCandless,who runs the Stamp Man website from Lytham, is advising anyone who has the coin to sell.
He said: "If you find one, sell it quickly as I think prices will settle
down and drop back in value.
"At the start with these things, you do tend to get a bit of a feeding
frenzy and prices can go artificially high.
"At the end of the day,the price will be linked to the number of coins
out there. I'm sure they will maintain a value of around £100 but it won't carry on at that price and it could take 20 years for it to be back at high levels."
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