Found this teaspoon about 4 inch below and have cleaned it as carefully as possible. Tried to make out what or who made it to try and determine the age. Cant make anything out on the back of the handle, but it looks like symbol instead of writing:
English silverplate; the images are not good enough to make any sort of id, but it doesn't really matter. Mid to late 19th century and of no value past sentiment.
Don't think it's silverplate. Those are hallmarks on the handle and the metal is corroded, not discolored. Suggest you search hallmark site. Very interesting design...