Some further informations about the Hebmüller-Admirals, I've found once a time in an Opel-Club-magazine:
In 1938, Opel charged only RM 1,795 for the Standard Kadett. The Admiral cowl chassis, built in very small numbers, sold for RM 4,200 alone!
There were four different six-seater-bodies available at Hebmüller suiting the Admiral-chassis. Prices:
Inside steering limousine RM 4.240.-
Inside steering convertible limousine RM 4,520.-
Pullman limousine RM 4.380.-
Pullman convertible limousine RM 4,660.
That shows a total of around RM 8,500 for a Pullman-Limousine, equivalent of 4 ½ Kadett Standard!
Really pure luxury. Hebmüller built only 20 Pullman bodies. With the beginning of World War II Opel stopped producing the Admiral series.