Sadly most of the machines from the great Duesenberg history in competition are missing,
Source: Incl. the text.jpg's on this page : Automobile Quarterly Vol 30, nr.4 summer 1992, p. 98-99 (Duesenberg Special)

Russel Mack directed me the other day (January the second 2007) to: http://www.museumofamericanspeed.com/Collections/Engines/ModelABE045.shtml
This museum possesses one of the few (two?) left Duesenberg Desmo Engines. In the mean time the museum staff took some pictures from the valve train, revealing after so many years for the first time the real design of the system. Unfortunately the system is NOT desmodromic, although it has two cams and two cam-follower portions per valve. One roller for the opening command and one without a roller for the "closing" command. Since there is obviously not a fixed connection between rocker and valve, the closing command is to be regarded more or less a safety measure or a Delayed Tension Valve System DTVS like the Jan Muller system.
In a DTV-system the valve spring has zero or some KG pretension and therefore can reach higher rpm without eating up the cams.
Pictures [by Susan Curtis] used with kind permission from the Smith Collection Museum of American Speed.

Picture of Fred Duesenberg the DTV System designer