This photo is, apparently, from Atlantic City in 1939, so we’re celebrating the 80th anniversary of the photo. Topless male swimming had become the norm around 1934, and I’m guessing that Atlantic City was just a little behind the curve, normalising it in ’39, hence the photo.
It’s almost certainly staged in front of a real sign, playing on the fact that the woman is pointing out the info given while the beach lifeguard looks bemused.
In many parts of the world, 80 years on, women are still fighting for equality in this matter.
Ella