Walter Matthau was 71 in Dennis the Menace when he played the character 'George Wilson'.
That was over 31 years ago in 1993.
In 2000 he died aged 79, starring in 85 films in his career, 17 of those after Dennis the Menace was first released. If he were alive today he would be 103.
In Dennis the Menace, I think Walter Matthau looks: