This is only the case for some 1950 British Coins.
Proof coins should be worth more simply due to the amount of work required to produce them. Proof coins are produced in a finite quantities for a given denomination and year.
An "Uncirculated" coin is one that goes through the usual minting process, but is removed before it starts banging and scraping against other coins and developing the marks and scratches associated with circulated coins. Uncirculated coins are an unknown quantity after they leave the Mint since they can be so easily circulated and subsequently lose the grading of "Uncirculated".
It is a matter of "supply and demand". Less "Uncirculated" coins for a given denomination (or year) are known to exist than Proof coins of the same denomination (or year), therefore the collector value of the "Uncirculated" coins is greater.
The same apparent disparity of value occurs for many coins and years.
Only the proof and uncirculated versions sold from the mint have more than face value.
These coins are still potentially in circulation so, unless they are part of a Proof or Uncirculated mint set or are individual Proof or Uncirculated coins and in absolute mint condition, they are worth 50 Pence.
The American Eagle Gold coins are made in Uncirculated and Proof versions. Circulated means exactly that, it has been circulated and or used. We do not use any gold coins at all in every day business. Proof coins have a highly reflective, mirror-like surface. The surface of a uncirculated coin does not.
The larger pre-1991 5 Pence coins were withdrawn from circulation and demonetised in 1991. So, unless they are part of a Proof or Uncirculated mint set or are individual Proof or Uncirculated coins and in absolute mint condition, they have little or no value. The smaller (18 mm) coins from 1990 onwards are still potentially in circulation so, unless they are part of a Proof or Uncirculated mint set or are individual Proof or Uncirculated coins and in absolute mint condition, they are worth 5 Pence.
These coins are still potentially in circulation so, unless they are part of a Proof or uncirculated mint set or are individual Proof or uncirculated coins and in absolute mint condition, they are worth Two Pence.
All years of issue of the British decimal Twopence coins are still potentially in circulation so, unless they are part of a Proof or Uncirculated mint set or are individual Proof or Uncirculated coins and in absolute mint condition, they are worth 2 Pence.
There were no British 1998 10 Pence coins minted for circulation. There were some minted for Proof and Mint uncirculated coin sets.
These coins are still in circulation so, unless they are part of a Proof or uncirculated mint set or are individual Proof or uncirculated coins and in absolute mint condition, they are worth 20 Pence.
With the exception of the 1994 50 Pence coin which has been withdrawn and demonetised, any British coins minted in 1994 are still potentially in circulation so, unless they are part of a Proof or Uncirculated mint set or are individual Proof or Uncirculated coins and in absolute mint condition, they are worth whatever is indicated on them.
The term Proof actually refers to a method of manufacturing that produces coins with very sharp details and a mirrorlike surfaces and are called Proof coins. Uncirculated or Mint State coins are coins not released into circulation and have no wear on them.
Isle of Man coins follow the dimensions, metallic composition and history of the equivalent British coins. The Half New Penny and Half Penny coins, the larger pre-1994 5 and 10 Pence coins and the larger pre-1997 50 Pence coins have been withdrawn. Unless they are part of a Proof or Uncirculated mint set or are individual Proof or Uncirculated coins and in absolute mint condition, they have little or no value. All other coins are still potentially in circulation so, unless they are part of a Proof or Uncirculated mint set or are individual Proof or Uncirculated coins and in absolute mint condition, they are worth whatever is inscribed on them.
Probably nobody. These coins are still potentially in circulation so, unless they are part of a Proof or Uncirculated mint set or are individual Proof or Uncirculated coins and in absolute mint condition, they are worth 2 Pence.