Found a nathen m5 for sale for around 200. I have not looked at them yet in person but from the pics they seem to have some pitting/corrosion. I’m just wondering if they would be trouble to recondition and if I can still get parts etc. here are the pics I have. Thanks Jared
You may need to get some professional help to restore them if they look as worn on the inside. Maybe try getting in touch with Mike Muha (South Bay Horn Works) on the Horn & Whistle board - he’s got great reputation for restoring these kinds of horns.
On the other hand, if they still sound OK, you could just scrub them up and repaint.