I was not brave enough to put it in the SE/30.What does Slotinfo or TattleTech say about the card?

Some VidCards disabled internal video entirely. Could be 8-bit grayscale, but if it's a simple rehash of an SE card you're likely looking at 1-bit B&W. Is that enough VRAM for grayscale?No, I don't think the card is faulty but the SE/30 may default the main monitor to the non-existent external display.
I don't think this is a colour card as it is missing any kind of DAC. Do you have another real multisync screen that you can hook up to the card?