Eighteenth-century London instrument workshops drew their brass partly from a trade in stolen metal

In eighteenth-century London, scientific-instrument makers such as George Adams sourced brass from foundries clustered in specific districts — Aldersgate, Moorfields, and Bishopsgate, and around Snow Hill and Shoe Lane. According to a peer-reviewed Science Museum Group Journal study of the trade's economics, this legitimate supply network ran alongside an illicit one on the same physical routes: "tradesmen settl[ed] their foundry bills in part through credit for old metal, while a brisk trade in stolen brass, often along the same routes, was fed by theft from workshops and storerooms." Theft of raw and worked metal from the makers' own premises was routine enough to count as a named feature of the supply chain rather than an occasional loss.

The point of interest is the entanglement: a prestige craft producing precision optical and mathematical instruments partly depended on, and partly leaked into, a criminal market in second-hand metal. The recycling of "old metal" for credit and the fencing of stolen brass were adjacent activities, hard to separate at the point of purchase.

This is a mundane-infrastructure counterpart to other cases where the precision-instrument trade could not fence its own knowledge or materials — compare claim-lippershey-1608-telescope-patent-denied-as-too-easy-to-copy, where a telescope's construction was too simple to protect. Here the leak is physical rather than informational: the metal itself circulated out of the workshop and back through the market.

The claim also sets up a legal bridge. Because a stolen brass instrument or component had real resale value, such a theft sat squarely inside the property-crime statutes of the period — see claim-englands-bloody-code-made-petty-property-theft-a-capital-crime — which in turn provoked the jury workaround described in claim-georgian-juries-undervalued-stolen-goods-to-avoid-the-death-penalty.