If I were to restore an older mercury vapor cobrahead, this would involve removing the original paint and repainting the housing. Does the original paint on older cobraheads contain asbestos, lead, or any other dangerous materials? I will be careful, I just don’t want to endanger myself without knowing.

If you are not sure, better assume it does...

Even when I have no exact knowledge about that at all, taking precautions assuming it does contain that stuff may be inconvenient, but wont hurt that much if it does not contain it. But the opposite may have bad effects...

I have no doubt the paint at least contains lead.

Depending on the age of the light, lead is definitely a possibility. Asbestos , I'd say doubtful ! To be on the safe side , wear a good quality dust mask or respirator when sanding and during dust removal. SAND OUTSIDE ! After sanding , clean the parts with soap and water and allow to air dry , when you're done , wash your clothes separately and take a shower before sitting on any furniture , etc. And lastly , wash your hands before handling food or drinking .

Yeah, wear a good quality respirator with some sort of NIOSH rating (N95 or better) during sanding is always a good bet. You could also use paint stripper to avoid sanding but make sure to do it in a well ventilated area, and wear gloves designed for use with paint stripper while scraping the paint. I believe generally lead paint was discontinued around the late 70s for home use but paint designed for luminaires may have had lead for longer so you still might want to take these precautions.

Asbestoes is generally rarely found in cobraheads, as most of the gasketing on the older cobraheads was mainly rubber.

Industrial use paints used lead way longer . The paint manufacturer we use at work only quit using lead based pigments a few years ago . So , depending on who the cobra-head manufacturer gets their paint from could STILL be using lead based pigments today .

Industrial use paints used lead way longer . The paint manufacturer we use at work only quit using lead based pigments a few years ago . So , depending on who the cobra-head manufacturer gets their paint from could STILL be using lead based pigments today .

I is not that much about pigment, but the base coat use active rust inhibitors. And the most effective chemicals known so far for this task are unfortunately lead compounds (I think it was called Minium). That makes the lead so frequent on older outdoor items.
By the way this is the reason many things seem to corrode way faster than they used to: It is because (maybe except some special uses) the lead compounds were banned and there is no known replacement for these compounds, so the present lead free paints are way less effective in protecting against corrosion. So if the thing does not feature another corrosion proofing method (Zinc galvanization,...), it is destined to have way shorter life and disintegrate by corrosion.

The main source of the problem was, many times people ignored to cover the lead based base coat by some sealing final coat (because "it is not needed, the base coat protects it good enough", ignoring the function of the sealing final coat is to seal the poisonous lead inside, not rust protection), so the lead was leached out by rain and poisoned all around...