I know that in the 1930’s Lucas often incorporated the date of manufacture in their serial numbers so the first dynamo could well be July 1932 and the other March 1934. I don’t know what the letters relate to.
It was also common practice for Lucas to stamp the direction of rotation on dynamos, magnetos and distributors. As far as I know all MMM dynamos have the same rotation.
I have been a bit late in picking up this topic. I am a bit confused about the relationship between ROTAX and LUCAS DDS dynamos. Are they, in reality, the same? My spare dynamo is stamped:- LUCAS DDS 6 12V 6848 B29128 5 31
I have presumed this is a correct dynamo for a J. Is that correct? Jeremy Prince J2 MJ3111