Why doesn't the NEMA tag say 40 on it? In fact it isn't even a true NEMA tag, just looks like one of those stick-on mailbox numbers. At first I though it was a 40 watt HPS, which doesn't exist, and doesn't need to thanks to 35w lamps. I guess the real NEMA tag faded out or was nonexistent...

Most likely it never had one, older fixtures didn't. It was likely then retrofitted to HPS and they didn't have any real NEMA tags so they stuck the number 4 on it.

I'm learning more about streetlights every day! As you can tell, I'm a "newbie", but have always been fascinated with lights, especially household incandescents.