Prior to 1930:
Prior to 1930 H-D VIN numbers were a bit erratic and model number designations changed frequently. Unfortunately there is very little information out there for these numbers and what information is available is not always very accurate.
From 1930 to 1962 the VIN number was the engine number and was only located on the left case. The VIN was between 8 and 10 digits with the first 2 digits being the production year, the next 2 – 4 letters being the model designation and the last 4 digits being the production number