To the original question, that looks to me like a composite filter, it's a porous hard media that filters just as well, if not better than paper, it's also much more stable under high pressure and heat. I'm willing to bet there probably wasn't a spring in there, just that chunk. We've got high pressure air filters here at work that are made from sintered bronze. Imagine thousands of tiny brass strings about an inch long bound together. There's nothing wrong with it, it's actually better than paper elements, and probably more expensive too.