However high end silver plate such as Christofle (France) does retain market good value (say 25-30% of its replacement value) and to a lesser extent in Canada, King's Plate (was Birk's best until a number of decades ago when it was discontinued) followed by Regency plate (used to be Birks best until discontinued a few years ago).
Of course the grand exception to this rule is sheffield plate which was widely manufactured in the late 18th century and into the early 19th century. Sheffield plate was invented Thomas Boulsover (circa 1743), when he accidentially found that silver will fuse to copper when sufficiently heated. Boulsover then continued applying silver to small copper items by this process. Joseph Hancock in 1755 then took this a step further by fusing the silver to copper in sheets thus allowing larger more elaborate pieces to be made. It became common place by around 1770 when the double sandwich was created, wherein a silver sheet is fused to both sides of the copper (often a combination of copper and brass). Sheffield Plate was used until electroplating was common place in the mid 18th century. Sheffield plate was made by fusing a thin sheet of sterling silver (92.5% silver) onto copper in a hot furnace, which was then rolled and hammered into a sheet.
This left copper showing on the edges which was either soldered over (early and rare) or covered with a u-shaped wire. Generally due to wear on Sheffield plate over time, the copper can be seen in edges and/or corners.
Most decorations on Sheffield Plate was flat-chased (hammered) rather than etched. Etching would cut into the silver thus exposing the copper. Note: Often coats of arms were etched exposing the copper underneath.
Most pieces of Sheffield Plate have a visible seam. If this seam does not exist then it may have been replated by in all liklihood it is not Sheffield Plate.
Furthermore pieces hallmarked "Sheffield Plate" are NOT Sheffield Plate, rather they simply are electroplated in the city of Sheffield England.
A good website showing Sheffield Plate marking: http://www.silvercollection.it/oldsheffieldhallmarks.html
When submitting a silver plate for online evaluation, appraisal we need:
1) Provenance: The item's history and where you obtained it from.
2) Measurements/dimensions in either inches or centimeters.
3) Digital photographs giving the front view and back view. And if possibleprovide us with a photograph of the company mark on its base (you will need a camera with a good macro lens). If you cannot provide a reasonable picture of this hallmark, then describe the marks as best you can and we will do our best to help you along.You can also try rubbing a piece of paper with a pencil over the mark, which may allow you to read and then photogrpah the mark.
As with all on-line evaluations, appraisals, the more of the above informations that you provide, the more accurate our onlineevaluation, appraisal will be.