I hadn’t considered ‘Chobert’ rivets; I’m too used to the automotive world and, seeing them only from the outside, they looked like pop-rivets to me.

One of the reasons I noticed them in the first place was that they looked out of place with the otherwise flush and / or blind rivets that usually populate aircraft fuselages; I also wondered if they’d ‘whistle’ as the slipstream passed over them!

Now pop-rivets usually end-up blind, but Chobert rivets, if I remember, are never ‘blind’?