Lucky Cuss - I will second what John has said. The "rules" for Kleeberg 2Rs are a bit out of date because Sheffield Plate was not well known as a counterfeiting method when that study began. I think Sheffield Plate deserves a place at the table. It was a popular and very successful method used in the UK and also in the US.
There has been a tendency to assign late dates of manufacture to Sheffield Plate coins, particularly those made in the US. I only partly concur with that as appropriate. Kleeberg was most focused on counterfeits that circulated in the US in colonial times. A coin from 1800 does not fit the bill. The US existed at that time.
However, if you include the early US Republic (Federalist ear) you get a different mix of potential methods including Sheffield plate and coins dated after 1789.
The one aspect of Sheffield Plate that Kleeberg seems to have missed was that there were shipments of raw Sheffield Plate that were made to the US in the colonial era. Meant for use as plates, cups, bowls or other pieces - the raw material was in the Colonies before 1789. So theoretically the smaller scraps of Sheffield Plate could have been diverted to counterfeit production.
Leaving speculation aside, your coin actually falls into a different category. I do not believe it is necessarily a Sheffield Plate coin. It is clearly a two layer production with a silver color metal over a darker core. But when you look at the details of the coin, they appear to be thicker than they should be. They are also not as sharp and lack fine details of a struck Sheffield. I believe you have a cast coin that was subsequently plated in order to pass for silver. The added metal thickens the details and reduces sharpness. The method of plating is uncertain.
The casting molds used appear to use a genuine host coin as a starting point. That raises an issue of what matrix (molding material) was used to create the impression. Casting liquid metal into a mold before the mid 1830s necessitated a mold usually made of fine sand and clay. After the mid 1830s other types of materials and new methods became available in very rapid succession. I think your coin could not have been produced before 1835 unless it can be proven to be a Sheffield Plate. I believe such a coin could still be produced today using old techniques and you could achieve the same appearance.
That is the crux of the issue on cast coins - age. Usually age of a casting is very uncertain. The mold dictates appearance and old techniques can still be used.
Cast counterfeits are not included in Kleeberg because of the issue of dating the point of manufacture. For the same reason, most cast copies were eliminated from the GNL numbering system. The ones that made it in were either extremely early casting types (sand cast) with apparent wear from circulation or in a few cases were known to be over well over 100 years old based on provenance. The oldest provenance I could trace for a GNL coin was 1830.
Your cast coin should be tested with XRF. The silver layer tests hopefully will determine how that silver layer was applied and of course the core metal should be tested to see if the components were all normal in period alloys of the same type. Most often trace contaminants will exclude coins as contemporary (because of inclusion of rare earth elements found in modern recycled metals). XRF can not provide positive proof of age only the possibility of age based on the trace elements included.
I do agree that the coin is interesting, it should be studied further and it should not be treated as junk.
Posted 12/13/2016 6:11 pm
