Looks like the NEMA tag is wearing off.

I like these fixtures, they are pretty well made, look good, and I hardly see ANY have the door missing! Only two out of the entire city of Denver I have seen have been missing the doors. And Denver is covered with these.

Still they could of done something better with FCO's, as they have too big of an angle.

What's that strange thing on the arm?

it's to reduce vibration.

Those are often most often found on Elevated Highways and Causeways...because the whole road would kinda shake as cars pass by....

I drove on an Elevated Highway in NYC and saw a bunch of roadway floods with those vibration reducers on the poles.....

I remember reading somewhere that excessive vibration is especially damaging to HPS lamps.

HPS and Philips lamps XD

I guess that thing absorbs vibrations?

There are always vibration reducers on powerline wires next to the insulators on high-voltage power lines. They aren't only on streetlights.

It seems to be common for the numbers to wear off the NEMA tags on the model 25. I've seen it happen to ones here and Niall's 25 seems to have slightly faded numbers.

Now the question is how do those devices reduce vibration?

It's magic. I really have no clue. That's a good question though.....
EDIT: Maybe these absorb the vibration? Seems like a kind of far-fetched idea but it's possible....