Help Identifying Royal Oak

[asb396]

Hi All - If there is anyone that can help me identify this Royal Oak which was just offered to me. I cannot seem to find a serial number on the caseback in the attached pictures, nor can I find a similar caseback on any RO. I also find it interesting that the clasp is stainless while the rest of the watch and bracelet are gold, although I have seen this before. Thank you in advance for your help!

All the best,

Adam