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 https://alchetron.com/Jim-Mooney