Yes, it is weird; the hour meter came on higher-end models at that time.
I was unable to spin the valves by pressing on them, but the exhaust valved failed my brakeclean test. It was a dribble, not a large leak. The intake valve passed.
I removed the valve to have a look. I wiped the seat with brakecleaner and took a picture; I think the seat is OK. The valve face has crud on it, so it no longer seated properly, but it doesn't appear burnt. When I clean the face, I will know more. I will carefully clean the face, lap the exhaust valve, and then perform the brakeclean test again.
I estimate the number of hours is under 400.