Hi, Bob
I just happened upon your blog, read with great interest. One of the illustrations shows an inscription by Robert Blass, and if I read your notes correctly you indicated you have not identified him. A quick visit to the Met annals will help you; he sang a large number of bass roles in over 20 seasons at the Met, quite an impressive list of roles and number of performances. I believe he was sometimes referred to as "Roberto Blass."

Andy Karzas