Personally I would include it just so that the next homeowner doesn't curse you when they go to drill something into an expected stud that isn't there.
What's his work like? Reading some of the descriptions on his site it sounds like it has some horror elements.
Loss of 3rd party data sales from the tracking embedded in their apps would be my guess.
Try threading a wood screw into the hollow pin until it grabs, and pull it out while twisting with a pair of pliers.
Earl Snell Memorial Park in Arlington on the Columbia. There was a bunch along the southern edge of the park.
This would make a good community, post news stories and have other people try to predict conspiracy theories about them!
That's what caught my eye as well! Anyone who's worked with qc or metrology would probably not be able to miss it.
It's a flexible coupling for a drive shaft. It probably does show up on stepper motors for 3d printers. It's used to allow for some misalignment between the motor and the rest of the drive assembly so there isn't any damage to the motor bearings or binding of the shaft.