Those who read the story in the recent E-Sylum about germs and money may also be interested to know of DeLaRue's long-standing recognition of the importance of numismatic hygiene. In 1937 the company patented a process to develop antiseptic banknotes that it claimed were “incapable of carrying infection”.

I'm not sure what prompted such an innovative leap forward but their patent application outlines a number of techniques designed to impregnate the paper fibres with a germicide during the manufacturing process. These include introducing the chemical during the pulp beating process; passing the web through a vapour chamber or applying it with the sizing. In each case the antiseptic (described here as being “intimately incorporated” into the paper) bears the rather formidable name: ‘methyl-hydroxy-tertiary-butyl-benzene'.

I can't comment on the potency of the compound as trying to find a layman's description on the the internet is a labyrinthine task but there is no mention in DeLaRue's application of the possible side effects of handling a chemically saturated substrate in such quantities as might concern the average shop-keeper or bank-clerk.

The company filed another substrate patent in 1962 - this time for a process that embedded a radioactive isotope into paper so as to identify and authenticate banknotes via an inimitable radioactive “signature”. Again, there's no mention of effects on the punter but the radioisotope proposed by DeLaRue in the patent is C14 - used in carbon dating to determine the age of plant and animal fossils and so I assume (as a non-chemist) that its effects were as benign as the company's good intentions.

If anyone would like to follow up, the relevant patent numbers are: 467,664 (antiseptic banknotes) and 990,256 (radioactive banknotes).