RARE Antique Chelsea Derby Transition Piece c.1775 Painted Mug Florals & Cobalt For Sale

I've done so much research on this fascinating piece and the more I work on it, the crazier I get. I believe it to be a transitional Chelsea Derby Mug which would date it around 1770-1775 to 1784. I've compared the painting on this piece to all the painters known to be working there at the time and have come to the conclusion that I have no idea who painted it; whoever he was, he had an incredible eye for detail. It is signed IW and an I, back then, was used for a J, but that hasn't gotten me anywhere. It's amazingly heavily painted; you can feel some of the painting.
William Duesbury, proprietor of the Derby Porcelain Factory , acquired the Chelsea Porcelain Factory in 1770 heralding the so-called Chelsea-Derby period of porcelain production until 1784 when the factory at Lawrence Street Chelsea was demolished. William Duesbery eventually merged both the Chelsea porcelain and Derby porcelain factories. Porcelain wares were marked with a combination mark formed from the Chelsea anchor mark and the Derby D mark. The first wares produced are generally indistinguishable from other Derby porcelain wares and this period is generally called the Chelsea-Derby period. The merger lasted until 1784, when the Chelsea factory was demolished and its moulds, patterns and many of its workmen and artists where transferred to Derby.
Use your own deduction about this piece and I would more than welcome any input anyone can give. I have found two of these mugs with this shape, but one is in a museum and the other is damaged; both have the same cobalt top rim but neither has such a pretty lower cobalt border. This one is flawless, but for minor gilding loss ! It measures just under 4" tall and is 4.5" wide. Enjoy !!!!!
Be sure to check out my other listings. I'll be glad to combine shipping when possible. Thanks for looking!