A paediatric galvanic pendant made by Richardson. The central section reads “Magneto galvanic battery childs size” on one side, and on the other “Patented in the US Feb’ry 3rd 1880”.

The small current known to be created by juxtaposed metals was thought to be therapeutic and spawned a host of quackery devices based on this theory of “Galvanism” in the late 19th and early 20th century.

• From the Phisick collection