I took apart the headset on my '83 Miyata 610. It is a basic cup-and-cone type, as you would expect. All four bearing races/cups show some wear (see pic). Basically, there is no "pitting", but the chrome plating is worn off in a very consistent thin line where there was contact with the bearings. It is not even easy to see, but I can feel the missing chrome with my fingernail. Bearing rings themselves appear to be fine.
So, can I get another thousand miles out of it, or is it shot? I will not be riding in the Tour de France, but do hope to take some trouble-free overnight tours.
Hey, if it is toast, how the heck do I get the old upper and lower head cups off of the head tube? They do not appear to be threaded....