This is a very young Mario del Monaco singing the second part of the duet with Santuzza in Cavalleria Rusticana. Year is unknown. It is lip sung but the track is unbelievable. Best MDM high notes I have ever heard.
1952, Opera Cameo Chorus and Orchestra, conducted by Giuseppe Bamboscheck, with Rina Telli and Richard Torigi. (Source info provided by commenter, Remo Mazzetti)