Yea this can be a confusing issue when dealing with Silverplate, But since the only way to replate would be Electroplating, I feel it would really destroy the value IMO. a lot of old sheffield plate has been replated, and can be hard to find untouch pieces, at least what I have read in my books. Old Sheffield plate is made by fusing a layer of silver on copper in sheets before the item is made. I found a tidbit on Wiki that gives a basic ideal of Sheffield plate and how to possiblely spot a fake. Thought I would add this to help up learn a bit more about the difference between Silver Plate, Sheffield Plate, and Old Sheffield Plate.
The Sheffield plating process is not often used today, as after about 1840 it was generally replaced with electroplating processes, such as that of George Elkington. Electroplating tends to produce a "brilliant" surface with a hard color — as it consists of pure rather than sterling silver and it is usually deposited more thinly. Sheffield plate continued to be used for up to a further 100 years for silver plated articles subject to heavy wear, most commonly uniform buttons and tankards. During the 1840-50 period hybrid articles such as sugar bowls were produced with the body being Old Sheffield and complicated small parts such as the feet and handles made from electroplate. These are rare and seldom recognised.
Much Old Sheffield seen today has been re-plated, especially items which received much use and polishing such as candlesticks. Items seldom displayed or used, such as egg cruets or soufflé dishes, are often in excellent condition and so may be confused with electroplate. Collectors should be aware that many designs have been reproduced in electroplate, with those from the early 1900s being the hardest to recognise since, like the original items, they seldom have a makers mark. The way to recognise the genuine article is to look for signs that it was soldered from pre-plated metal sheet or wire rather than constructed in base metal and plated afterwards. Look carefully for soldered joints, often well-disguised by the experts of the time.
The term "Sheffield Plate" is widely used these days by those dealing in electroplate produced in Sheffield and most collectors prefer to use the term "Old Sheffield Plate" to identify the early fused plate product described on this page. Another misuse of the term is in describing "Close Plated" ware which was generally made in Birmingham in the first half of 19th century. Close plate consists of silver foil soldered onto a steel base and was used for items such as candle snuffers or cutlery requiring greater strength than fused plate.
