Ruth I found out the striped bar is called a crest, on 3D carvings etc it's a plump ring like a shepherd's hat, on other items you also sometimes see them decorating crowns. There's quite a few families with swan crests but I've not found one with the outstretched wings either side yet. I did see some buttons on the buttonmonger website with the same metal rim and fabric shanked back however, so it's looking like this might be the oldest button yet! those were 19thC, I'm wary this looks a bit too new though?