Any difference between Edmund's & Edmund's Custom

Finally found a Edmund's finned head to match the dual intake for our Plymouth flathead 6. Question is, the intake is marked "Edmund's Custom" and the head is marked just "Edmund's". I heard many years ago that the earlier castings were marked with just "Edmund's" and the "Custom" part came along later. Any truth to this? I have many pieces for the Ford flathead and it is all marked with the Customs name. Also, anyone know about how many Plymouth flathead Edmund's heads were cast? I know it wasn't many.