Has anyone seen fixtures where the lamps arc tube was completely black.

I did see a MV NEMA head near the golf course the other day. It’s a Westinghouse or ITT that’s missing the refractor, and I priced it has a clear MV bulb in it, but the tube is completely black. It does light at night, but barely dim enough to light the ground.

When I was young, one of my neighbors had a Handyman with a clear BT28 bulb (I'm sure it was a Sylvania) that had a really blackened arc tube.  Funny thing is I don't really remember that light being used all that much.  It was mounted on a pole made from a small, peeled log and powered by an extension cord plugged into the block heater outlet. 

I’ve seen some metal halide lamps with jet black arc tubes that still gave satisfactory light. Always amazing !

If it's a HPS with a completely black arc tube then the thing is on its last legs, or might be running on a lower voltage or improper ballast- enough to allow it to keep going for now.