It's a keeper for sure. It looks like a 26" frame, the tire should have a size on it. The stem doesn't look like a Schwinn stem, it looks like a run of the mill kind, so it was probably forced in there. If Araya51's method doesn't free it, I would put a big pipe wrench on the end and try to hammer it up off the frame. If that didn't work, I would cut it off close to the frame, not cutting any of the frame, then using a hacksaw blade, slice it on the inside until you cut through it. That would be tedious to say the least, but would leave the frame in as good of shape as it can be. If the stem is only a few inches long, that would sure help, but the usual 7 or 8 inch length may be stuck in there.