From the Pegasi Numismatics vcoins store:
http://www.vcoins.com/ancient/pegasi/store/dynamicIndex.asp

                  CONSTANTIUS I CHLORUS 305-306 AD. Gold Aureus (5.18 gm) of 
                  Siscia as Caesar 293-294 AD. Laureate head / Hercules clubbing 
                  Hydra. RIC.3(R5). VF+. Extremely Rare.

                  CONSTANTIUS I CHLORUS 305-306 AD. Gold Aureus (5.18 gm) of 
                  Siscia as Caesar 293-294 AD. Laureate head / Hercules clubbing 
                  Hydra. RIC.3(R5). VF+. Extremely Rare.

                        Price 
                          US$ 4,950  € 4086.58
                         £ 2833.69
                         AUD$ 6489.51
                         CHF 6379.63
                         CAD$ 6028.11

                        Rates for 7/21/2005