Some of these coins were one-offs to be fair, the last James II plume shilling on the market that I know of was Spink SNC in the early 80's - £2,500 for a coin in only fair condition if I remember rightly.  There might have been another sale since but none I know of.
 
	"Conceivably the finest known" is not the case for the 1700 plumes 6d - perhaps "finest known in commerce" might be more accurate, as being a duplicate of the BM's, the BM 's retained one would be better and the Ashmolean has a better one as well: