https://www.auctionzip.com/auction-lot/Two-Vintage-Thonet-Bentwood-Chairs_8EE498CAEB
You can see what this pair of vintage Thonet chairs sold for !! Your chair was before they went with Thonet !!
Mundus was just a furniture company same as many here in the US !! However Mundus eventually merged with Thonet` so sales would be a little higher !! How much ?? No one can tell !! Worth of anything depends on what someone is willing to pay !!
My guess would be about $30. USD on a good day !!