Throughout the prototype period, the various models were given series designations (as noted above), and presented to the RLM as the basis for series production. The Luftwaffe never took Heinkel up on their offer although the company decided to build a total of 25 of the aircraft one way or the other, so with 10 down, there were another 15 of the latest model to go. In keeping with general practice, any series production is started with a limited run of "zero series", resulting in the He 100 D-0.