Take a little look, self ballasted lamps will have a filament near the arc tube, if coated try shining a light from torch and try to make the filament out.Just a thought putting a multi meter across the base you should get an ohms reading where as normal it would show as open circuit, correct me if wrong?
The filament: But be aware some designs used a short piece of incandescent filament wire in lamps requiring ballast as an oxygen fuse, to protect against UV when the outer bulb breaks (the filament normally glows, but once it comes in contact with oxygen from the atmosphere, it burns so breaks the circuit). The SBMV have the filament really long, with a few support wires (it is to be rated at nearly the full mains voltage, after all; the fuse uses to be rated at just barely 2..5V or so, so really very short).
And the ohm-meter method works only for 120V lamps, not for the 230V ones. The reason is, the 120V lamps are of preheat start, so a bimetal starter contact shorts out the arctube and keeps just the preheat filaments in series with the ballasting filament (so the circuit is complete when cold). After power ON, the auxiliary filaments preheat the cathodes, so the main arc may strike.
The 230V designs use the regular auxiliary probe start burner design (from standard burners these differ only in the current and voltage rating, otherwise their concept is the same), so the circuit is open at low voltage, same as a regular SBMV.
By the way the filaments within the arctube ends is another "giveway" of that lamp being a 120V SBMV. No other MV uses filaments inside of the arctube, they use just the auxiliary probe with a series resistor.
I think the most reliable method would be to "google" the type number. Even when really some obscure outdated type, google usually will give some usable hint (e.g. just the region, so you know what to look for - preheat filaments for 120V SBMV or long ballast filaments for 230V SBMV,...)
