Thanks. The maker is not in any doubt. It's 100% the mark of George B. Sharp of Philadelphia, with the lion
s passant having no official meaning. He's listed as using that mark on both silver and silver plate, but most of his output does seem to have been silver:
View attachment 2189942
marks and hallmarks of American and Canadian sterling silver, coin silver, solid silver, silver plate makers, with makers marks, location, history of American metalware makers SAART BROS COMPANY, SACKETT & CO LTD, G.T. SADTLER & SONS, SALES STIMULATORS INC, H.I. SAWYER, SCHOFIELD CO INC...
www.silvercollection.it
British silver does not carry the lion passant as the only mark. It's part of a
compulsory set that includes the mark for the assay office, a date letter, and (when applicable) a duty mark as the monarch's head. None of those are present on this piece (and the duty mark was required until 1890).
I agree that this might well be silver (as acknowledged in my revised opinion) and, I too, would be able to say for sure if I had it in my hand. I don't know of any reliable way to tell if American pseudo-hallmarks are for plate or solid silver apart from via company histories, or when they have an accompanying word mark such as 'sterling', 'coin' or whatever.