Lucas used a comprehensive numbering system, which can be a bit unwieldy at first, but it is worth getting to grips with. Each type of item (e.g. dynamo) that they produced had a model designation (e.g. E3LM), which can be decoded and is explained under each section. The 1936-57 Lucas catalogue lists 18 models of dynamos. For most models of dynamo there are several variants, each of which have their own ordering number even though the difference might be only one part, this results in 72 different dynamos from those 18 models. The model designation and the ordering number are invariably stamped onto a major part of the component as well as the month and year of manufacture.