Amazing Spider-Man #75 Aug 1969
"Death Without Warning!"
Spidey, aware that Dr. Connors and his family are in danger from the Maggia, searches for them;
The once-elderly Silvermane tries to convince Marko and Cicero that he is in fact a younger version of himself

while Dr. Connors escapes and Spider-Man arrives;

In the ensuing free-for-all Silvermane just keeps getting younger.

Script by John Romita (plot) and Stan Lee (script), pencils by John Romita (layouts)
and Jim Mooney (pencils), inks by Jim Mooney