I’m probably the worst Shore-born person to try to explain beach badges, because I don’t remember ever owning or using one. (I only go to the beach during off-seasons, or after dark. My mother and I gave up our Annual Trek to the Beach™ sometime in the mid-1990s.)
As far as I know, beach badges are little… badges… with a pin… that proclaim you’re a paying beach customer. Some are daily passes, some are seasonal passes… you know.
What I find interesting is how little they’ve changed over the years. This particular display started with 1948 and went through to 2001; all the badges consistently used the same little squiggly pin.