Um, whether it's rated for both depends on what sort of power supply it has in it.
I haven't bought an STC-1000, but my 110v WH-7016c - which looks awful similar, like same designer and factory similar, has a 110v to 12v transformer in it, and then a 5v regulator for the logic bits.
If the STC-1000 220v version has a 220v->12v transformer, with no 110v tap on the transformer (meaning we can't cut some traces and solder some wires to convert it), hooking it up to 110v might result in ~6v on the low voltage side, which would be enough to power the logic but perhaps not enough to throw the relays on and off.
If you post high resolution pictures of both sides of the board, I can tell you if it's likely to work or can easily be converted.
But yes, in my experience, chinese ebay sellers often fall into two categories. 1: Sellers who resolve your problem double-quick with no questions asked, 2: Sellers who don't give a crap until you threaten negative feedback, and then resolve your problem double-quick.