Those things are a tough as old boots, I had a beat up 20 watt one years ago that only had ONE spring left in the "verb tank & it still sounded killer. I remember someone in the Netherlands posting about having one fly off his bike & land in a canal..after fishing it out & letting it dry it still worked!!
I taught at a local school that had the KB version, it looked like it had been drug behind a car for oh say 500 miles..still worked & sounded fine.