I agree with smurfy it looks like the pin that locates the ring failed and allowed the ring to turn until it got into the exhaust port and caught. It’s one of those things that happens with age. Detonation or overheat can cause it prematurely. Looks to me like the rings had a serious amount of blow by. That can lead to increased piston crown temps, and detonation at the locating pin area. You may be able to re use the cylinder. The rods look typical and aren’t a concern to me. But a thorough inspection of the crank would be wise.