You can have my iron buckle when you pry it from my cold, dead pants

I just noticed that many lists of prohibited weapons at parades or demonstrations include, among many other things, "iron buckles." (The Cleveland limit on weapons outside the Republican National Convention included this, as did limits outside past conventions in other cities.) And New Orleans actually bans them outright:

It shall be unlawful for anyone knowingly to … [s]ell, manufacture, purchase, possess or carry any blackjack, sandclub, metal knuckles, switchblade knife or spring knife, iron buckle, zip gun or stungun.

I thought "iron buckle" must be the name of some specific weapon, like "brass knuckles" or some such, but my Googling came up empty. Is it just a specific weapon that's little known (at least under that name), or no longer used? Or are you really not allowed to have belt buckles made of iron in New Orleans?