Year was the reissue year, not the performance: this is the San Francisco Opera performance of 3 October 1975 (live KKHI broadcast). San Francisco Opera Performance Archive, https://archive.sfopera.com/il-trovatore/1975, lists Il trovatore on Sept 12/17/21/27/30 and Oct 3 1975 under Bonynge with Sutherland, Obraztsova, Pavarotti, Wixell, Grant, Roark, Burgess, Davies, Duykers -- the same cast held here -- and marks 3 Oct as the live KKHI broadcast. The Bella Voce CD issue in the folder (BLV 107.216, back cover and booklet scans) prints "San Francisco, October 3, 1975" outright.