If you are trying to tell the difference between the P4 Standard, and the P4 Advanced, or Pro, then look at the air vents on the underside of the 'arms'. If there is a more or less solid grid then it is the P4 Standard. The Advanced, and the Pro have space between the slats of the vent. Look online for pictures of both to get the idea.
If you then determine it's not the P4 Standard, then look for side sensors as noted by others.
There are many Standards being sold as Advanced and/or Pro models. I researched that difference to distinguish by picture.