Vinay (born 1912) actually made his debut as a baritone in 1931, singing Rigoletto, Scarpia, etc. In 1943 he started singing tenor roles - Don José, Otello, etc., also Tristan, Parsifal, Tannhäuser and Siegmund at Bayreuth. Then in 1962 he went back to baritone - Telramund at Bayreuth, Falstaff, Dr Bartolo(!), Falstaff and Iago. Harold Rosenthal in Opera Grove says "his artistry, intelligence and musicianship were always in evidence", which I guess includes his late baritone roles.
It'll be interesting to see if Domingo the baritone, also a famous Otello of course, emulates Vinay by singing Iago!