I believe this is exactly the as fitted to Alvis Speed 20 models that used dual ignition. I has three positions, the middle for "Off" and one either side for either mag or coil. The spindle comes through the back to be connected to the H.T. change over switch on Alvises.It is marked "AM" under a crown but it is not an Air Ministry mark as far as..
Nice clean unit with nice clean numbers on the dial. 150 Kilometers Per Hour. After the 135 there are three more marks. Total 150 KPH.Postage in Europe is 15 euro. WorldWide postage is 25 euro. Please see my other ads.
An original Bosch ignition coil, marked TF6/1. It is key operated (no key) at one end and has 6 connections on the bakelite end. Complete with original mounting bracket. Buyer pays shipping costs.