Ron,
The lazy "S" is an enigma and the closest to logical explanation that I have heard is that it represents the laydown pattern of a flamethrower. A few Freikorps Flammenwerfer units had a skull and crossbones insignia.
There is no evidence that any Leib Hussar units had DH marked Lugers. I have only encountered two Lugers with Leib Hussar grip strap markings and they did not have any chamber insignia.
Cheers,
Other Ron