Great Britain 1 Pound KM#993 2002 [решено]

I have low quality Great Britain 1 Pound coin clearly dated 2002.  The observe shows Elizabeth II with tiara right. The reverse shows the Royal Arms with supporters. Krause (2019) lists this nickel brass coin with dates 1998, 2003 & 2008. This is the same in Numista (#7385). Did Krause & Numista simply omitted the 2002 year, or is this mule (error) coin? Any information is appreciated.

 None of the above. It is a fake, hence the low quality - 

one of the reasons the Royal Mint switched to the 12-sided pound coin. 

 It is known that forgers disregard what design goes with what date. 

That's interesting, the coin is a good copy! I have more coins of these heraldic series and some of them in a similar state. Thanks for the information.  Fun have a fake.

Fake coins are the reason why this coin was withdrawn, there are just too many of them.

Just to give a little more information on just how widespread the counterfeiting issue was [Copy/Paste from an older comment of mine]:

The old round pound coins were heavily counterfeited. This was one of the major driving forces behind the switch to the new 12-sided coins.

The Royal Mint stated, in May 2015, that around 2.55% - roughly one in 40 - of all the round pounds in circulation were fake. In May 2014, they had stated that the rate of counterfeits was 3.03% - roughly one in 33. I can't find the exact original survey article (Google links to the modern page speaking about counterfeits of the new 12-sided pound), though there are plenty of newspaper headlines from around that era repeating the statistics.

The Numista catalogue is complete for UK round pounds. You can see the official list directly on the Royal Mint, which is reflected on Numista. https://www.royalmint.com/discover/uk-coins/coin-design-and-specifications/one-pound-coin/

If you have any mis-matched years & designs - they're fakes.

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You can also see a small list of known forgeries here on Numista (Exonumia) - your specific year isn't there, though 2001 is: https://en.numista.com/catalogue/index.php?e=united-kingdom&r=&ct=exonumia&im1=&im2=&ttcf=y&cat=y&ru=&ca=6&no=&v=&i=&b=&ie=&u=&a=1990-2050&dg=&m=&f=&t=&w=&mt=&g=&se=&d=&c=&wi=&sw=

EDIT: https://assets.publishing.service.gov.uk/media/5a7f8dc6e5274a2e8ab4cdff/PU1775_cover___prelims__FINAL_.pdf
In the above report commissioned by the UK Government talking about the new one pound coin, they state in section 1.1 that the rate of forgeries had increased even higher to one in 30!

Thanks for the detailed information, I was not aware of this.