Patek Philippe

I would very much like to know what are the differences between the two references. I understand two different metals are used, one is wg, what is the other? Has any forum members acquired this Patek, and what are your thoughts. The pictures are beautiful... 

Hi, If I'm right there's only one reference 5180/1G, the "/1G" meaning that it has a white gold bracelet. Cheers Dje