Does it thread on either way? Or does the “tick” provide some locking feature? If it distorts the threads enough to lock it.
Are you sure those are AN parts?
To me, they look almost like someone tried to peen the nut after installation as a locking mechanism. Either that or a defect.
I keep my aerospace hardware in separate cabinets. These would have come from 1 of 2 possible sources...
To be clear, these nuts have been purchased but not installed. This is a new build.
Thanks for all the input everyone. This is an interesting one!
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I just re-read Vic's chapter on jam nuts and I don't see anything about the tick mark. Maybe he'll see your post and chime in, but I'm guessing it's not relevant.