I would suggest that what you have is a normal XK that has had the XK60 bodykit fitted at a later stage (unless you have owned the car from new)
The X150 version of the XK appeared in showrooms in March / April 2006, the press cars were late 2005 as far as I can remember.
The bodykit fitted to the 2008 XK60 'special edition' was available to buy as a dealer fit accessory to 'retro fit' onto any 4.2 XK.
If you let me have the last 6 digits of your chassis number, I can run the car through our system at work to find out the original build spec and designation ?