This pretty free-form band measures approximately two and a half mm, give or take as the pattern ebbs and flows, and would make a fantastic spacer. The pattern is organic and continuous: I think it could be sized pretty easily, though, with a little bit of care on the part of the jeweler. It measures as a size 7 on my mandrel. Although it’s not hallmarked, I’m pretty sure it’s 18k and would guarantee it as 14k, but I’m pricing it considerably below that, at least until I stop being lazy and order a gold-testing kit!
ETA: Gave up while I was writing this and ordered the gold-testing kit, so I'll confirm or adjust early next week.