I have no dog in this fight, but I have seen the AV mark identified in this thread by Oel and Huszas as an Austrian import mark from the mid to late 19th century:
viewtopic.php?f=21&t=31066I assume their information is correct as it comes from a published source, and if so it would be excellent to include this mark in the forthcoming updated Austrian section.
In my admittedly very limited understanding of Swiss pocket watches, Voumard made ebauches--indeed, down to the 1960s. It seems unlikely to me that an ebauche maker in the period in question would also make cases. It was also extremely common for Swiss-made pocket watch cases to bear multiple hallmarks (in addition to Swiss hallmarks) in anticipation of their export throughout Europe and even further abroad, although in this case I think we can assume the Austrian mark was stamped upon import.
At any rate, the maker of the ebauche is really the key here and if the maker of the watch is indeed Voumard, then the name should be clearly stamped on the ebauche as well as the case.
I leave it to others to make some final determination.
Regards,
DR