This is a classic old recording (originally recorded 1953) of the operetta and is excellent. It is mono (1953!) and hence to young ears can sound limited but the performances are excellent. I am an operatic tenor and the quality of Gedda's singing is superb - note the second part of his duet with Valencienne. Add excellent idiomatic orchestral playing, a superb Hanna (Schwarzkopf) and Vieniese abandon in the chorous and it has everything.
As a boxed CD set the later Maticic recording (under the control of Walter Legge) is outstanding but not as idiomatic as the Ackermann. If you love old Vienna, just sit back and enjoy! Incidentally, also dirt cheap as an MP3 download, too.