take a pic, then view the exif.
you could check file number on the cam, but that could have been reset.
The exif wont lie.
Thanks Monkey, correct me if I'm wrong. To view the EXIF on the D300, you press "play" to view the photo on the LCD screen then press up or down on the cursor pad until it shows the EXIF?
Shak, thanks mate but I will need to be able to check it at the shop so won't have a PC with me to down the photos.