Don't confuse the panel enclosure with the panel bus assembly. Panel enclosures are often listed for use at different voltages, and will have a generic one-label-fits-all covering all the applications that enclosure is used for. It doesn't mean that it IS either of those voltages, just that it's listed for it and could come with either voltage. You'll need to check and see if that panel is wired 120/208Y or 120/240V 1-phase.
