Aaand such riveted mail needs to be kept from rusting, with light oiling with a rag and tight storage for when it's not mail-schlepping season. Household clothing bins with tight lids are good.
Also takes about four times the man hours to weave it, compared to butted mail. And it comes out around half the weight compared to butted 14 gauge (.080") mail. Quite a differeence, and very nice. Also full bragging rights -- I got the real sh... shtuff, here!
Black annealed tie wire, .0631" diameter, then.
Annealed, it's very soft, squishy like lead. It's a good feedstock for heavy, hard duty riveted mail, and I use it that way myself. I wouldn't use it for butted links, as it's not stiff enough to hold up, but you can really knock it around in making links and piercing -- drifting the hole open, technically -- for riveting with teensy bits of wire or flattened wire to make "triangular rivets." Well, yes, they're triangular; they look like tiny pizza slices. Pointy end goes in first and is upset, rivet fashion, to clinch the links' overlaps between the upset point and the broad end.
General purpose riveted mail is optimally of rather thinner mild steel wire, at around .048-.050" wire diameter. A good balance of weight and protection -- and you pretty much have to go to a welder-supplies shop to get wire that diameter, and anneal it before you form it: hot work. Mild steel welder wire in that diameter or close to it is the stuff you'd want, and it comes springy, so must be softened with a good hot baking.