Do I have an authentic vintage Rolex Geneve Cellini Watch?

I have a vintage Rolex Geneve Cellini watch. It has a round iridescent blue dial and a white metal bezel (white gold?) The case back is stamped with the words "Stainless Steel and Water Resistant" It has a number stamped on the back: 490912. There are no numbers present under the watchband strap at the 6 and 12 o'clock positions. How can I know if this is an authentic Rolex Cellini watch?

placeholder text for bug in Chrome