My Sophie Anne used to eat the metal zippers out of pairs of jeans, at least once or twice a month. I thought she just chewed the zipper out and hid it somewhere, not until years later did I find the opener/closer in her poop in such a manner that it did not just happen to fall there...
I even found little individual teeth in it too. Took her in for X rays, which were positive for zipper ingestion, but due to her history of eating them and never having a problem, the vet opted to let it all pass naturally... which it did. He said it could be a mineral deficiency, but never put her on any supplements. She passed away at 16 years old, 10 years ago.
She died from Osteosarcoma of the jaw.