swap meet temp gauge wiring?
 

i just got a niehoff temperature gauge at a swap meet for $10. the problem is i dont know how to wire it. the two bolts for the bracket are the ground, but the only other 2 bolts are connected by a piece of metal. is this a resistor of some kind?
http://img32.imageshack.us/img32/1715/dsc0724m.jpg
http://img96.imageshack.us/img96/8216/dsc0722oa.jpg