A small group of Fire Guard pose with a (small) trophy. Probably the winners of a local competition there is an interesting helmet marking on the chap bottom left. I'm unsure currently what the extra letters relate to. It looks like a P and an L. The gentleman bottom right does not seem at all pleased with the proceedings...
Going by the information on this letter, the PL on the helmet almost certainly refers to "Party Leader". Seems there's quite a lot of hierarchy in the Fire Guard here - Sector Captain, Party Leader and then Sector Clerk.
News about interesting insignia, ARP related info and period photos that turn up.