Pipepedia says it originated in 1986 and was then discontinued at a undetermined date. Then a small revival was issued in 2006. But the White Spot page shows it is now once again available. So, technically, it is a new finish.
I like Brian's suggestion that they ran out of the letter 'r' hence county and not country. However - and I have no evidence for this conjecture - in England the 'County Set' were/are typically the upper crust country set - the sort who wear hunting pinks (i.e. red coats) when fox hunting; attend summer balls and generally mix with the 'right sorts'. So perhaps calling it 'County' was an attempt at suggesting a superior range suitable for the upper echelons of society.
Of course my theory could be a load of codswallop in which case hopefully some will correct me!