How old is the serpentine belt?

Reviewing the CarFax records for our car from before we bought it, it had:

75K service, includes "drive belts replaced" Since there is only one belt, it must have been changed. 2012
90.5K "water pump replaced" 2014

Both of those were at a Toyota dealer. When they replaced the inverter pump it said that, not "water pump" -presumably "water pump" is the one on the engine.

So it looks like they changed the serpentine belt at 75K. I would assume that they put a new one on when they changed the water pump, because it would be stupid not to spend the $20 (or whatever it was at the time) since the old belt was already off.

The car is now at 143K miles. So does the serpentine belt have 68K miles on it or 52.5K miles?

Hard to inspect this belt, I can only see about 3 inches of it from the top of the car. It is a bit shiny but no cracks visible on the outside. Can't see the inside from there at all. Tried to reach around the water pump from the top to get some fingers on the inside, but couldn't manage it.

 

Took a couple of pictures with the cheap Teslong endoscope. The first picture is from the coaxial camera (looking down, I think on the section where the belt is contacting the pulley on the pump, which is the grey metal above it), the second from the sideways camera (looking up, on the free section of the belt before the tension pulley [I think] before the pump). Lots of cracks but no chunks missing. The belt is about .42" wide, and it looks like around 5 to 6 large cracks per inch. The cracks open up a bit when the belt is on the pump, as that bends the belt backwards slightly. Guess I'll change it when I get back from a visit to the Bay Area. Hopefully it has another 1000 miles or so of life left in it! Also looked around the water pump and there were no signs of a leak, which is consistent with the observed zero coolant loss.