Browsing a Meccano Magazine back issue (the November 1924 edition), an advertisement for radio components caught the eye.
Specifically the coil pictured in the left-top corner. Hadn't paid much attention to these ads before, but last week a pair of coils for use with the crystal radio had arrived. (Ordered from the global bric-a-brac shop that is the internet).
The coil in the advertisement is labeled as the number 500 and this specimen is a number '150', but other than that it's the exact same type. Complete with frequency chart and the 'what the wild waves are saying' motto.
This neatly confirm that this coil is contemporary to the 1923 Edison Bell crystal radio set that it'll be kept with. This coil and another Edison Bell number 100 coil came plugged into a little tuning component, adjusting the coupling of two coils (De Forest).
The nickelled fitting were badly corroded and dirty, but as is often the case with nickelled parts they came back fine from an encounter with Brasso and a cloth. The black parts are hard rubber, these were simply cleaned and given a thin polish with vaseline to help preserve and make them look better.