The base with the toothed ring and spring (so that it can be rotated to get the clamp into a convenient position and have some flexibility on a moving vehicle) is Aerial Base No.2 and the insulator is made of ebonite (like the Insulator W/T 'B' used with the ground spike)).
The other one is Aerial Base No.3 and is a hollow rubber moulding with a heavy clamping ring for bolting it to a flat plate, and a brass socket with clamping screw and wing nut to take the aerial rod. It's rather bigger than the No.2, but doesn't require the cage for the spring mounting.
Chris.
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