It started to rust after about a year. No, it wasn't outside. I have just painted it with matt silver Hammerite anti-rust paint, and this has not altered the sound. The paint might chip when the bell is struck with a beater.
Note to Latin Percussion: Get it right, next time. And stop putting labels on your bells that say "The finest cowbells". The adhesive is a swine to remove. Do your advertising elsewhere.