Looks to me like some of your former tennants were growing weed with a metal halide bulb.

Looks MH to me, but, you cant use it without the special ballast. Since new 250W MH bulbs are about $20.00, I'd toss it in the trash.
HARDDON Reviewed by HARDDON on . Hi all just curious.. want to know what kind of bulb is this it says 250 watts I found it in one of my rental houses and if it is a good grow bulb where can i find a big enough socket that will burn it it won't fit into a grow shade i have. Rating: 5