I have this lamp that I can't identify because the etch has wiped off. I know it's likely a 400w lamp judging by the size of the glass envelope but what I don't know is if it's a clear MV lamp or a MH lamp. Any help in identifying this lamp would be greatly appreciated.

I see no starting electrode and an insulation sleeve around the support wire along the tube. Both are signatures of a (pulse start) MH lamp. No starting probe because these use HV pulses for ignition and the sleeve is intended to positively charge on its surface (by photo electron emission) and so form a field repelling (or prevent attracting them) Na+ ions from the arctube wall.
MV's are all started by a starting probe (except the Iwasaki/Eye MoonPulse MH retrofit lamp) and do not need that sleeve (Hg is inert towards the quartz, Na is very reactive with it when not bound to some halogen or so), HPS use ceramic arctube (Na is highly reactive with quartz and/or most glasses, forms brown opaque staining and makes them to loose strength).

Next step is to determine the burn position.

This lamp has the white enamel at both ends...usually that means universal burn position.