Technology Of Silver-Plated Coin Forgeries

Just some random thoughts on the subject.

I believe that the History of industrial and metallurgical technology is an area that was overlooked 20 years ago. That is a thesis I have held for over 30 years and have been researching for 20.

A clear understanding of exactly when and where technologies changed is a key factor in sequencing counterfeit types. Not all technologies available today or any point in time have always been available for use. The problem seems to be a real void of clear easily accessible answers to the questions of timing.

Mercury amalgam silver coating (which I believe in some early circles was referred to as silver washing) was about the ONLY technology that could be used to pass a counterfeit at some periods of time. It was definitely successful prior to Sheffield.

Painting I would guess was an option in some form although mercury as the liquid binding agent makes the amalgam a form of painting. But there are silver paints (or silver appearing paint colors that date back considerably.

True electroplating is a post 1830 phenomenon rather late for Colonial counterfeiting.

The Sheffield Process was only discovered in 1770.

So in 1760 what could a forger do? Hot dips in any metal caused surface errosion due to melting and basically a terrible looking mess for any POST-creation silvering. However, a hot dip process for a planchet was possible. The candidates for this process may be zinc (does virtually no damage to the planchet) can be struck post plating and looks decent for a VERY brief time.

Silver dipping creates erosion problems in the planchet and deposition thickness could be hard ton the host coin and there are problems with control of the surface layer thickness.

Tin dipping was a technology known earlier than 1760 used to prolong the life of some marine metals along with zinc. It is possible but I have not seen one (of course I have a few suspects that need testing - laying around someplace).

A copper coin can be dipped in mercury which will leave behind a thin plate resembling silver. It has problems when it forms a meniscus in small details but it could work. There was a forger using that technique in 1997 in Mass that made quarters for circulation. Mercury will leave the coin feeling wrong, will also evaporate aand is poisonous but all that a forger needs is the first pass.

There is the possibility of casting a planchet OVER an off metal core. It is a process that I suspect but have never confirmed. To work the core would have to be mounted inside each mold and silver poured in and around. The contact points at minimum 3 for stability would leave edge spots that would require work. It forces a struck counterfeit to be made.

I agree the foil strikes of ancient coins (fourees) was used. The principle was mechanical bonding caused by the strike pressure as the three layers were hammered together. This is similar to cold Sheffield plating which has the habit of peeling away.