Hi Theo..As Lex said the B30 had direct lighting to save weight. No lead acid battery was fitted..a small drycell battery inside the headlamp provided a 'parking/pilot lamp' facility...The electric horn was replaced by a bulb horn. The power was supplied by a magneto for ignition but instead of a dynamo an alternator was fitted on top of it. These lightweight bikes were the first to be so equipped.
The system was very low output though and was quickly found to be inadequate. Later versions were fitted with a conventional mag dynamo and from period photos it is apparent that at least some of the early models had a mag dynamo 'retro fitted' to them after removal of the set up shown in the photo...Ian
Thanks Ian that is verry clear i have a bottom end from a Matchless G5 1939 500cc and this was with a ignition coil and only a dynamo i think.mostly to make it cheap GR Theo