Old Sheffield Plate (or OSP) is the material developed by Thomas Boulsover in the 1740s, a fusion of copper and sterling silver which could be made into a range of items normally made in solid silver. The material rapidly gained popularity as a substitute for solid silver, as it was much cheaper to produce. Any object made in silver could be made in Old Sheffield Plate, although objects subject to heavy wear such as spoons and forks were not so satisfactory in plate.
The characteristic identifying feature of OSP is the 'bleeding' or 'show through' of the copper base, especially on points of wear although there is also a subtle difference in colour from the pure silver of electroplating to the "very faintly bluish lustre" of OSP. In addition to having a distinct bluish cast, the alloy produced in OSP is also harder than electrodeposited silver. The material remained popular until being replaced by the electroplate process in the 1840s.
