Funnily enough, the vendors on the ebay link you give actually describe theirs as Sheffield Plate, which I don't think is correct ... Sheffield Plate is an actual layer of silver on top of copper, and I think later pieces were a silver - copper - silver sandwich. I think that is why they are asking so much for it. Eveything that I've found so far for this company suggests that their pieces are electro-plated.
Someone will get a bit of a shock if they buy it thinking it's Sheffield Plate, but then again I think anyone who knows what it is wouldn't make that mistake.
Nevertheless .. you've got a lovely piece there...