Ummmm, you could short the PC plug with a paperclip? Use a camera without film in it? Look up the GN on Google?
I tried google, but I can't find the same model I have. It has no manufacturers marks on it, no guide number, wattage, anything at all. I only believe it is Spiratone because the power pack that came with it says Spiratone.
I guess I'll meter for 100ASA and figure it out from there.