First appearance of Black Widow’s skin-tight leathers.
It wasn’t until I started re-reading old Spider-Man and Daredevil comics that I realized what a major player Black Widow was in the Marvel Universe. She’d already been an Avenger by this time, and soon after this she got a regular gig on Daredevil (the title of the comic even changed to “Daredevil and Black Widow” for about a year).
Anyway, this was her signature look until Frank Miller redesigned her in the 1980s.
Also, look at this older appearance: She was basically Spider-Woman.