Any consumer of silver (or any other precious metal) places a great deal of faith in Assay marks on silver.
Assay marks on silver
Assay marks on silver guarantee to the consumer what fineness of silver an item is made of. In England the Lion Passant is one of the Assay marks on silver to guarantee that the fork you are buying is indeed Sterling or .925 silver. As we know, different countries have chosen to define silver at a variety of finenesses – the US chose .925, France went with .800 and .950, Russia is .875, etc, etc.
Assay marks are so important because of the simple metallurgical fact that copper, which is used to alloy silver to make it useable, does not color silver until the mixture reaches about 50:50. Without Assay marks the potential exists for a silversmith to be charging you for .925 silver when in fact they have only used .800 silver. Make enough forks out of .800 instead of .925 and you can make a tidy profit.
Can you think of an assay test that would work in a Pub?
So given this inconvenient fact, how do the people responsible for assaying silver conduct the test?
This question becomes even more interesting when you think of it in the context of the English hallmarking system. The Goldsmiths’ Guild has been assaying silver since 1327. Obviously non-invasive methods like mass spectrometry and x-ray fluorescence weren’t in use. Equally, fire assay – in which the silver is literally melted – could not be used, as destroying a piece in order to test it wouldn’t be a convenient system!
Remember in the English system a full set of hallmarks shows the Lion Passant to denote sterling, a City mark to show it’s origin, a date mark, and the maker’s mark.
To those of you who aren’t British it may not strike you as odd that the mark for Birmingham is an anchor. It’s always seemed odd to me. Birmingham is an inland city, an anchor does not seem geographically appropriate.
So why is it used? Because in 1773 the Goldsmith’s Company held meetings and eventually established the ‘Assay Office’ for Birmingham and Sheffield in a pub called the Crown and Anchor! Legend has it that a toss of the coin gave the Anchor symbol to Birmingham and the Crown to Sheffield. The pub was home to the Assay Office until 1815 when it moved location.
Obviously, if business was conducted in a pub, they must have had a relatively simple method of testing. The answer is that they used a touchstone to conduct the test so they could strike the Assay mark on silver.
A touchstone is a piece of fieldstone, slate, or lydite, all of these stone have a fine grained surface on which the soft metal of silver leaves a visible trace. Different ratios of copper to silver will leave different color marks on a touchstone. So .925 will look different from .900, .875, .830 etc.
So in the Crown and Anchor our Assay-master would draw a line on his touchstone with pieces of a silversmith’s work, then compare the colors to a established sample. Once satisfied he would proceed to strike the Lion Passant, Anchor and appropriate date stamp into the piece and the public could purchase silver secure in the knowledge that you got what you were paying for.
If you are really curious, you can actually purchase a touchstone via (where else) Amazon. There seems to be a book with an assay kit available.
It did occur to me to wonder about corruption but after a bit (not exhaustive by any means) of research I could not find any mention of it in England. The Goldsmiths’ were given their Charter to regulate the silver trade by the Crown. I would imagine that if stealing a penny or two got you hung or sent to Australia (if you were lucky) then the penalties for corrupting the Assay system were sufficiently severe to deter just about everyone.