This watch is an 18K gold Daytona model 16518. It is a W series from circa 1995-1996 (Rolex serial number by date). The photo shows the correct locations of the hallmark/assay/makers mark, gold standard/common control mark, and karat mark. You can also see the location of the serial number and reference/model number. As with all watches at KeepTheTime, this watch is an authentic Rolex piece. Feel free to use it as a guide for your own solid gold Zenith movement Daytona watch.
More pics/video of this Rolex 16518 Daytona Zenith 18K Gold Watch