I got interrupted writing the last post and didn't see Matt's reply. When I read it, it jogged my memory, I too had a silver spoon that was plated. I don't have an image to hand, except one of the mark, that does show slightly that it was plated:
The odd thing about my spoon, is that the plating appears to have Chromium or a similar metal. I guess this was some misguided 20th century attempt to prevent tarnishing. If I come across the spoon I'll take some images of it, but at the moment I haven't go a clue where it is, but it does go to show that strange things happen sometimes!