The previous notes have presented details of the reference collection of counterfeit shillings of George III dated 1816-1820 and a description of the pieces in terms of the appearance of the metal. This note will present a few typical pieces from each group along with a few outliers and determine the metals using XRF analysis. The results confirm the three main groups of counterfeits; (1) ‘tin’ based, (2) the ‘copper alloys, brass and copper’ pieces and (3) the ‘silver’ pieces that are genuine coins. Two odd-coloured silver pieces have been found to contain significant amounts of nickel, a metal not used in coinage applications until after the 1850s. Many of the pieces show traces of mercury (200-500ppm) likely from previous silvering, though is only just above the Limit of Detection using this XRF machine. Those pieces with complete silvering show the highest mercury contents (>3000ppm) suggesting the silvering was created using evaporation of a mercury-silver amalgam.
Counterfeit Shillings of George III 1816-1820 (iii) Metallurgy – Gary Oddie
BNS Research Blog 
This article was very interesting especially being I have just acquired a George the third cartwheel restrike that was silvered so this process especially the above nickel mentioned is really helpful. Thank you. Wayne Kulesza