Yes, check for cracks on both sides of the belt (flat and corrugated), signs of fraying at the edges and see how hard and brittle the rubber has become. That will give you some indication of how old it is.
If you don’t know when it was last changed, change it anyway. The 944S engine has what is known as an ‘interference’ valvetrain, which means if the timing belt fails, the valves and pistons are going to hit each other. Normally at the very least you will have bent valves and head damage and at worst piston damage which could mean a rebuilt engine.