Strange "grit" on 964 Turbo interior cam-box housing...

[cstreit]

Doing a top-end on a 964 Turbo today and I noticed what looked like weird casting grit on the inside of the right side cam-box housing. I rubbed it with my finger thinking it was sand-cast marks, it came off!

I then scraped some off with a blade and it appears to be a fine-grit buildup inside primarily the right box, almost as if it were flung off the sprocket/chain in this area. Not a "linear" pattern per se, but only in that area around the sprocket.

The engine definitely missed a few scheduled oil-changes, but I've never seen this on any 911 engine, even the real rats. Is this some peculiar part of the casting that "wears off" over time? Anyone seen it before?

Thanks!