I think it's older than 1976. By that time the grilles at the bottom weren't so tall, and the handle also appears to be an earlier '70s style. I also question the grille being the same color as the rest of the fridge. In my experience, they have always been either silver or black.
$500 is pretty steep, unless they're embedding the real cost of shipping in that price. Just based on the exterior, the fridge appears to be anything but pristine, but it will still probably run forever.