Duke D'Omas/Mad

The Gilded Duke
It has been suggested that the Gilded Duke and the Duke D'Omas are one and the same person.

There is at least one case in the comic where one person is referred to by two different names, without an explicit connection between them being established in the comic itself: Dr. Dimitri and Dr. Vapnoople. We know, though, that they are the same person, because the Cast of Characters on the Girl Genius web site has an entry for Dr. Dimiti Vapnoople. Thus, the precedent is established for at least the possibility that they both could be the same person.

The walking gunboat on which Moloch von Zinzer and his brothers served was golden in color, and Moloch also noted that the Duke D'Omas paid his minions in gold.

This gunboat had only very recently been destroyed by Bangalesh DuPree on her last airship mission before her first appearance in the story. No explicit timeframe is given for the amount of time between the fall of the Duke D'Omas, and when the von Zinzer brothers decided to give up raiding the countryside to keep their clank in good repair.

If we assume that this was sufficiently difficult to do that it was very likely that they spent less than a year terrorizing some villages with their walking gunboat before deciding to set out for Paris, then the timeframe would appear to be consistent with that given for the defeat of the Gilded Duke.