Berg's involvement with the project would later be the cause of allegations that Zeppelin had used the patent and designs of David Schwarz's airship of 1897. Berg had signed a contract with Schwartz under the terms of which he undertook not to supply aluminium to any other airship manufacturer. He later made a payment to Schwartz's widow as compensation for dissolving this arrangement. Claims that Zeppelin had been influenced by Schwartz were denied by Eckener in 1938 and also rejected by later historians. Zeppelin's design was "radically different" in both its scale and its framework from that of Schwarz.