This is one of the latest hearing devices in the collection and the only electronic one. The Earmaster 550 Hearing Aid was manufactured in 1965 and contains an integrated circuit.
This custom made in-the-ear transistor hearing aid was moulded into a casing which was then gold plated. This was to increase cosmetic appeal rather than for any hypo-allergenic benefits. It did not catch on and 1965 was the only year it was made, which makes it rather rare. The gold casing is engraved 5VLOC.