I found a couple of stainless ones in the same condition as you've shown, on the ground where my boat is now on the hard due to other problems. (so from another boat)
I guess they must have been in contact with a nobler metal as the screw adjusters were OK (usual prob) just the band rotted through.
Flexi hoses resting against something? An update bringing something too near? You can't be too careful.
I guess it's a case of doing your own maintenance regularly, and keeping all your senses on red alert.
I use red hermetite on pipes when assembling, and even with the clamps off, it's difficult to separate the pipes from their spigots after a while in use.