Mallory "half keystone" rings?
I think I've already answered this through a process of deduction, but I'll throw it into the pit for confirmation / discussion.......
When I got the new (Mallory) pistons for the Merc rebuild, the pistons have parallel slots for the rings, wheras the rings themselves are what I can only describe as "hybrid" - one face parallel, the other on a taper (keystone style). No "top" markings, so using conventional logic, will go in either way up.
But they're not symmetric, so presumably one side is favoured as the top. One was broken on reciept, and the replacement (again asymetric) had a dot. I'm not going to say on which face so as not to bias any opinions.
So, the question - Taper face towards the spark plug or the crank?