P8 is actually a USP, this is a Mk 23. Yes, they look very similar, but you can tell by the accessory rail. On the Mk 23 it stops before the trigger guard, on the USP, which is about an inch shorter, the trigger guard begins before the rail ends.
While it does look a little big to be a P8, mark 23s dont come in anything but .45. It says right on the slide 9mmx19 plus it has a P8's Bundeswher (spelling?)markings.