GK, the art nouveau bags hold very little. They hold far less than a constance. They are about 7 inchs by not very many inches and they are hard to get open. I think they were meant for a handkerchief, some "mad money" and maybe a key and a couple of calling cards. They would easily accommodate a smart phone and very little else. I carried one of these bags to a gathering and I couldn't get the darn thing open or was it closed? They open by a turnlock but it has a little doo-dad to secure it. The doo-dad's the problem. Also, they're not very noticeable, being small and having quiet colors.
But I like tooled leather and eventually, I figure I'll find a bag that's a reasonable size. Because, you're right, tooled leather would look cool with some autumnal tweeds.