Summary

This is a trivial belt loop, the kind that is captive on the buckle end of the belt to help to capture the tongue of the belt. I think the original came unsnapped and fell off somewhere in airport security in Seattle.

No experience yet to see how durable it is, though I'm hopeful with the filament running around the loop.

At 1mm thick with a 0.4mm nozzle, Simplify3D used three loops. The middle one might have been undersized; I might have been better off at 1.2mm thick.

[ Update 8 Sept 2018 ]
That first one (made out of PLA) finally failed after about 10 months of almost daily use.