Many Philips radio's are using two different segments of wire on the drum of the variable capacitor to tune to the various stations.
The steel wire type forms one half and the "cotton" tread closes the loop, AM and FM circuit are using the same type of different wires.
The steel part is on vintage radio's subject to corrosion and breaks easily, I found it no problem to replace the steel by a "cotton" type.
Question: what is the reason Philips engineers have chosen for this two type of wire concept?