I posted this in the general British coin forum but noted with interest that 2 days ago Noonans sold at auction what is evidently an extremely rare decimal coin. It may be the rarest of all currency from the decimal era!
This would be the 2009 10 pence, uncirculated currency piece with the lion reverse of 2007 and earlier. Out of curiosity I looked it up and could only find record of a different piece sold at London Coin auctions about 8 years ago and then vague mention of one other specimen from a 2008 (!) currency specimen set, I think it said for babies born that year or similar.
Regardless, I didn’t even know this coin existed - maybe because I have focused on the later milled pre-decimal coins of 1837-1970. Do readers know more?