The number of coins released for popular 50p designs has now been confirmed by the Royal Mint, and there are some new contenders for the rarest 50p design currently in circulation.
The Royal Mint's mintage figures reveal how scarce popular designs from 2017 are in reality, including the Sir Isaac Newton and Peter Rabbit coins.
Which? explains the newly released mintage figures, and the other factors you need to take into account.
New 50p designs tend to be particularly sought after by collectors, but it can take up to a year to confirm how many coins have actually been released into circulation.
The Royal Mint has now confirmed how many coins of each design released in 2017 were minted.
The 2009 Kew Gardens coin remains the rarest of all, with just 210,000 in circulation.
By contrast, the extremely popular Peter Rabbit 50p was minted 19.3m times, making it comparatively common. Coins from the same Beatrix Potter series released last year, including Tom Kitten, Jeremy Fisher and Benjamin Bunny, had smaller print runs.
You can see the full list in our graph below.
The mintage indicates how many coins of that design were created and released, and so will give an indication of how commonly a coin will pop up in circulation.
The lower the figure, the harder the coin is for collectors to find, meaning they're likely to pay higher sums for it.
For this reason, mintage figures can have an enormous impact on a coin's perceived value in the market.
A Kew Gardens coin recently sold for £80 on Ebay after attracting more than 17 bids.
However, mintage is not the only factor that counts towards a coin's worth.
Some coins have high mintages, but the design carries sentimental value, so that even non-collectors may be tempted to hold on to it.
When people hold on to coins, or add them to their collection, they are effectively withdrawn from circulation, making them harder to find.
If a coin is older, it's also more difficult to collect, as coins are lost over time.
By this index, the 2012 Olympics coins - particularly the football, triathlon, judo and wrestling designs - are among the most sought after, though Kew Gardens remains on top.
Keep in mind that a coin's condition will also be important. If it's been in circulation and is scuffed, worn or dinged, a collector is unlikely to pay for it.
At this stage, the mintage figures for coins released in 2018 have not been made public.
The 2018 numbers are eagerly anticipated by coin collectors - although for 10p coins, rather than 50ps.
Around 2.6m coins were minted, but which design will be the rarest?
Change Checker has compiled records of which coins its members have collected and requested. It found that the Angel of the North, English breakfast and Loch Ness designs were most in demand.
Until mintage figures are known, however, it's impossible to say whether this reflects scarcity or enthusiasm for these particularly well-loved British icons.
The full A-Z of designs is below, so keep an eye out in your change.