Need help identifying unusual spot on Center/Rear Housing wear surface
 

I finally have gotten around to restoring my 10th Anniversary FC and today I broke down the engine. The car had sat for a long time and my main concern was the condition of the coolant passages in both the rotor housings and the irons. Thankfully everything looked to be in pretty pristine condition and no unusual wear was obvious on any of the surfaces until the light caught the center and rear irons a bit differently than at first. I noticed what appear to be vertical cracks on the contact surface on the ignition side that I can feel even with a rubber workshop glove on. I looked through the FSM manual that I am using for this teardown and Mazda did highlight that exact spot for inspection.

https://cimg3.ibsrv.net/gimg/www.rx7...e7c5d4fa6b.jpg


This is not a sharp edge but more of a smooth ridge and I have not had a chance to get a gage on it to check if it is within the specs from Mazda. The pictures are highlighting the line more than you would otherwise notice with your eyes, but it does show up on both sides of the center housing in the same spot and on the rear housing in the same spot. The front housing seems to be fine.

https://cimg8.ibsrv.net/gimg/www.rx7...ef09aaf209.jpg
https://cimg9.ibsrv.net/gimg/www.rx7...2cd4084e04.jpg

I have searched and searched on here for anything similar and have not had much luck. The funny thing is that the engine ran strong with fine compression before it was ultimately parked and stored.

1) Is my suspicion correct that these are cracks? Was this caused by detonation (considering it occurred near the spark plugs)?
2) Are the irons still usable? I am assuming not, but would be relieved it they could be (I fear that finding new ones is going to be a challenge)

Thanks for any help that you can provide.

Hard for me to tell from the pictures, but it that looks more like normal side seal wear than cracks to me. Finish measuring the wear areas per the FSM, and go from there based on the numbers you get. If they are a bit past the side seal wear spec, there's the option of sending the plates out to a shop that can lap and re-nitride them which would make them like new, if you can't find new or suitable used plates to use.