I can't reply via the JA return link site, not responding normally, so I have to reply in the usual way for email exchanges, which is herein.
The other actor in that sequence was not significant and I don't remember. I have seen that same minor sequence of that same unknown movie quite a few times over the years, so I am sure it was Lee J. Cobb after all. I compared the sound of his voice, his laugh, his cry and his proportions, height, shape, etc. to known roles of Cobb and they matched perfectly well. I am just as sure as can be and driving everyone crazy as usual.
I met Lee J. Cobb once when I was a high school student. It was in 1975 or 6 and he was in New York making a movie or something for TV, but that was him and he is the same as I remember him from the movies.
Don't start at the bottom of the ladder in searching for these answers, go right to the very top because we had experience and answers such as, "Did you try imdb.com," is ridiculous. We went all the way to the point of contacting his family or close friends & co-stars, but never did because we had no way of asking for them.
I believe it is a touchy subject, so best to be careful when asking and know whom you're asking before venturing any further.