This is more or less just a curiosity/useless trivia kinda question.
I just came across this pic while reading some SAE papers and I can't say I've ever seen the metal plugged one. Did this ever make it into production?

 

who has the pattent on the left one, i dont think ive ever read about it

 

There is no mention of the corner seal at all other than the pic. The picture is in a chart that relates to methods to improve sealing.
It's on page 11 of 13 in SAE paper 2004-01-1790

 

The rx8 got something very similar.

 

Yep that would be it. The SAE paper was on Renesis development, I probably should have mentioned that.
I'm guessing these aren't compatible with standard 13B rotors and apex seals. Correct me if I'm wrong.

 

Not compatible mainly due to the height of the apex seal.

 

The side exhaust ports mandated the use of an iron insert in the corner seal. The rubber piece would just burn out with the exhaust gas coming in contact with it. It doesnt offer a sealing advantage in a non-renesis engine, the design was merely changed to cope with the side exhaust ports.

 

Wow, with all the regulations and health hazards with applying chromium I'm surprised they used that for a substrate under the DLC, I figured they would have used cobalt or nickel.

 

This is 100% true . Though a solid corner would have been just fin too IMO.

-J