I'm quite new on Numista and still playing around with very common coins (trying to complete a set of each 1p,2p,5p,10p, and 20p by year). Today we found a 2019 20p coin that is rather yellow compared to all others. The quality seems to be very good and the yellow-ish tint seems to be quite homogenous. Not easy to see the difference in a picture (yellow on left, normal on right), but is crystal clear looking by eye. Is this something relevant, or the coin simply endured a very specific chemical life?
Cheers