By definition, a true Grande Complication / Mechanical Contrivance. Looks to be 100% Peter Oberhammer design and I am not sure if he or his crew made it, but it wears all the hallmarks.. If you look about 3/4s of the way down(right below the rotating Mauser) you will find an artikel on a vierling( Ein vierläuflges Gewehr von Oberhammer ) but I guess Peter Oberhammer just scaled it a bit more.

https://www.germanhuntingguns.com/archives/oberhammer-peter-of-munich/

https://oberhammer-jagd.de/

I do wonder about the chamberings if they are in-fact correct?

Serbus,

Raimey
rse