Thanks enormously for checking, I should have said I had done so but I'm a new member and it was my first time using the database. The mug belonged to my father who had a collection of commemorative ceramics and his attributions seem to have been well researched but I wasn't sure on this one. Dad made a note to check Heritage auctions and indeed I've found the image, several similar mugs have also been sold. The one Dad has isn't identical in all respects - certainly not from the same printing plate and obviously no title on the piece. Yes it could be a few years later than 1780 but isn't a modern piece. There is a mug showing the Duke of York in my father's collection, the horse and rider's pose are similar but the face and hat are quite different. But I know facial accuracy wasn't a feature of these pieces. Thanks again, Rob. PS if the screenshot I have uploaded is a risk to you because of breach of copyright, feel free to remove the image and anyone can search Heritage Auctions for "George Washington" Mug. I guess we can also post the url https://historical.ha.com/itm/political/3d-and-other-display-pre-1896-/george-washington-rare-equestrian-figure-mug/a/6066-38016.s?ic4=GalleryView-Thumbnail-071515