the stamped mark is interesting isn't it? I wonder what period it dates to, to be handpainted and to have a stamped mark (retailer mark maybe?)
There is reference in the Harrach book to orders from Harrach for specific companies, but none are 'W & H' that I can see. I wonder who they were? maybe a retailer in the Midlands perhaps?
Walker and Hall is the only company I can think of and they were/are silver/goldsmiths in Sheffield - however the ampersand isn't designed in the same way as their hallmark (although there may have been earlier versions than I've found) and I'd have thought it may have been if it were for them.
m