About 10-12,000 hrs.
depends on what kind of shoe sole
Another factor the soil types where it has spent most of its working hours. From my limited understanding of soil science, east of the Rockies you have much bigger areas that will be similar. In the far west there are counties with twice the soil types as whole states in the east.
So shoe leather gets much more abrasive with the right mix of clay and sand. Just enough clay to keep the sand in place.
So it could very a lot from region to region. So you are very correct in questioning the hour meter.
I have a D6 that has hour meter readings scratched into the hood, I believe the highest is 9xxx. That is how it was in 82 when I bought it. Over a few years every area if the tractor was rebuilt. It was then my main tillage tractor for 500 to 800 acres a year plus a little dozer work for 30 years. Despite my efforts I never could keep a hour meter working, but 7000 to as much as 10,000 hour are my guess. The petals and deck has about the same wear as your picture. But my home area is very sticky clay with no sand. As another measure of ware the tracks that were new in 83, the bushings still feel round and have never been turned.