I could not see a taper on the black ring until I held it up against a square and then I could see a very slight taper like the middle ring in your picture.
Yes; it's a 'scraper ring'. A good [though it does have gaps] online reference on piston ring types is
HERE .
My other ring has a grey coating on the wearing surface but it does not look like chrome to me. Also it has a tiny 90 degree step at the top outer corner of the ring.
That's because it's '
hard chrome' plating, as distinct from the decorative 'bright chrome' you'd be familiar with.
I talked to the service manager where I bought the rings and he said the black ring goes on top and the coated ring with the step is the middle ring.
Oh dear. Grumpy's reference is correct; that service manager isn't. The top ring works the hardest; that's why it's an advantage to provide it with a hard main wear surface, expensive though that is. In comparison to a plain cast iron ring, at any rate.
