Here is a gray FPOLC/Sun-Tech photocontrol. The brass legs on this one are not curved like they should be, making it difficult to insert into a twist lock receptacle.
They're not curved? Be careful since the straight legs might pry the contacts in the PC socket apart and prevent normal PCs from fitting snugly if this PC is inserted/removed too much. I'd get two pairs of lineman pliers and try to make the bends yourself.
They are curved a little bit. Just not as much as they should be. I posted a pic comparing the legs on this one to another FPOLC/Sun-Tech photocontrol.