The ring is installed with a gap to accommodate thermal expansion. Otherwise it would get too tight.

AFAIK to check a piston ring you set it a certain distance into the cylinder and measure the gap. There's a specification for the gap. If the gap is too small (should only happen with new rings), file it wider. If the gap is too big, replace the ring.

The picture of the second cylinder has sharper cross hatching but the first one is also distinct. The difference might be in the lighting and photography rather than actual finish.

There is a prescribed clocking of the rings relative to the piston. The gaps of the top and middle rings should not align. Again, check the manual.

Have a machinist check the cylinder head for cracks if the engine overheated and you have low compression. In the 6 cylinder version of that engine, it is common to find cracks in #4 and #5 cylinder from the exhaust valve seat to intake valve seat and also to the prechamber tip. Machinists can find cracks in the head between the combustion chamber and coolant passages that are difficult or impossible to see with your eyes. such cracks usually expand with heat such as when the engine is running.

Sixto
87 300D