Uh, yeah, so keeping in mind that "haubert doublier" was supposed to be more protective than the baseline stuff, it's either chainmail (1) with heavier and larg

Uh, yeah, so keeping in mind that "haubert doublier" was supposed to be more protective than the baseline stuff, it's either chainmail (1) with heavier and larger rings, (2) with two rivets per link, (3) with two layers, e.g. one hauberk worn on top of another, possibly with a linen interlayer (4) with smaller and many thousands more rings, (5) with double the links in each pattern unit – effectively, two rings where normally there would be one. There's some scholarly support for each interpretation. The Romans were known to wear a double layer of mail, as their shoulder yoke overlapped their torso armor, though this predates the French and English by ~1000 years. There's also a good example of #2 here, though it's quite recent and not European: https://www.metmuseum.org/art/collection/search/35633 https://www.metmuseum.org/art/collection/search/35633 The most popular interpretation, among scholars, is #5. But there's no conclusive evidence. IIRC there was an effigy of a knight at the cathedral in York wearing double mail, but it was removed (and now thought lost) in the early 19th century. This is the sort of ubiquitous historical question that can be solved by an amateur.