Donald Pleasence was 50 in THX 1138 when he played the character 'SEN'.
That was over 53 years ago in 1971.
In 1995 he died aged 75, starring in 178 films in his career, 124 of those after THX 1138 was first released. If he were alive today he would be 104.
In THX 1138, I think Donald Pleasence looks: