They're just standard used struts with different (maybe lowered) springs... he says that the although the struts are used, just think of them as a free gift witht the springs attached, so you're just bidding for the springs really. He doesn't say much about the springs... but I'll hazard a guess and say that they're probably "low down" about 20mm or more lower than stock with a firmer rate.
If bidding goes much higher than 30,000 yen, I'd hold out for a proper set of coil overs... but then it depends on how much you've got to spend. Good coil overs from Yahoo kinda start at the 50 - 60,000 yen bracket, but then again thats for ultra-popular cars. Because you've got a Luce, the local guys here know how hard it is to get good used stuff for it, so every time you bid it might end up with the price getting blown out, I don't know.