Unfortunately this is NOT the correction conclusion IMO. Unless of course you took it to Luis Lalala of Aureo & Calico and he told you its 20thC fake. Which I seriously doubt! This IMO is a well made 18thC Birmingham Sheffield silver plated Contemporary Circulating Counterfeit. Overview: When analyzing silver artifacts or coins with X‑ray fluorescence (XRF), it’s important to remember that the technique is inherently surface‑sensitive. The X‑ray beam penetrates only a few microns into the material, so the reading reflects the composition of the outermost layer rather than the bulk alloy. This means that if the surface has undergone chemical or physical changes over time, the apparent silver content can be artificially elevated compared to the true internal composition.
One mechanism for this is silver surface enrichment. In alloys where silver is mixed with less noble metals such as copper or nickel, environmental exposure, cleaning, or corrosion can cause those base metals to preferentially dissolve or oxidize. Silver, being more chemically stable, remains and accumulates at the surface. As a result, the outer layer becomes richer in silver, sometimes approaching 90–95% purity, even if the bulk alloy is significantly lower. This phenomenon is well documented in archaeological coins and plated wares.
In the case of Birmingham or Sheffield silver‑plated items, the plating process itself deposits a thin layer of nearly pure silver over a base metal substrate. When tested by XRF, the instrument primarily detects this plating, not the underlying alloy. Thus, a reading of 95% silver is consistent with the presence of a thin but high‑purity silver coating. The same principle applies to period CCC (coin, collectible, or commodity) pieces, where repeated polishing or selective corrosion can leave a silver‑enriched surface that misrepresents the true composition.
This is why XRF results must be interpreted with caution. While a surface reading of 95% silver may suggest high purity, it does not necessarily reflect the bulk composition of the artifact. To confirm whether an item is solid silver or merely plated, complementary methods such as density measurement, deeper‑penetration techniques (like ICP‑MS or fire assay), or cross‑sectional analysis are required. Without these, XRF alone can give a misleading impression of silver content due to surface enrichment effects. See this reference - its not GNL listed but it could be a coin I would not mind doing more research on its metallurgical makeup. See this reference: https://www.amazon.com/Counterfeit-Portrait-Eight-Reales-real-Reales/dp/1500497177/ref=sr_1_1?crid=2ON96MNZYYND1&dib=eyJ2IjoiMSJ9.dfPszcETag57m7IW7mszl0aw2cATkohAHYlAEi3lMCCESgNHLhdWNXslFqZC3gN-jM1UZD6lQVqf7jiQUfQy8-AP6F8yfJGh-XGjBQPyg7g.QauDMUggGfUO0jfc-_yy6V1Vik_rD3_p_h-6p18v2Vw&dib_tag=se&keywords=gurney+8+reales&qid=1765304251&sprefix=%2Caps%2C112&sr=8-1
