Sometimes there will be a huge blower motor in the bottom. Other than that, about a pound of wires and some other motors with the occasional circuit board. I don't think I've ever encountered any brass, and I've done quite a few furnaces. If you really wanted to pull every penny out of it, you could probably take it completely apart piece by piece and sell it as short steel (or whatever your yard calls it). There's quite a few screws and some bolts holding it together, but it shouldn't be that hard. Sometimes, a few parts are salvageable and may be of use to a small-time plumber. Might be a good way to get a new contact.