Jan-Michael Vincent was 22 in The Hardy Boys: The Mystery of the Chinese Junk when he played the character 'Tony Prito (as Mike Vincent)'.
That was over 57 years ago in 1967.
This was his first recorded movie acting credit (although may not technically be his first actual acting role).
In 2019 he died aged 74, starring in 68 films in his career, 66 of those after The Hardy Boys: The Mystery of the Chinese Junk was first released. If he were alive today he would be 79.
In The Hardy Boys: The Mystery of the Chinese Junk, I think Jan-Michael Vincent looks: