This is probably Wilhelm Karl Königswarter (1866-1927). The Königswarter family were Jewish Austrian-Hungarian nobility from Königswart in Bohemia. Jonas Hirsch Königswarter (c.1740–1805) made a lot of money as a businessman and his five sons founded banks in Frankfurt, Vienna, Amsterdam and Hamburg. This has parallels with the Rothschild family, whose crest appears on the coat of arms in this bookplate - the five arrows, representing five sons, unless the Königswarters used it too. The family established the Königswarter Foundation in Merano in Italy in 1872 and helped establish the neighbouring Jewish cemetery. There were three other Wilhelm Königswarters, so it's hard to work out what this one did. He died in Brno in 1927, a month after the death of his wife, Rose Goldschmidt.