I bought a Riviera Genova steering compass several years ago, to replace my Ritchie compass which was stolen from my boat. Major reason was that it fitted (almost - 150mm dia. vs 6"dia.) and was the only one available at short notice.
It worked well, accurate, no adjustment needed, until a recent passage. Running before a building wind and sea, the autopilot wasn't coping well so we started hand-steering - the compass isn't working!!
Managed to get back to port without a compass (in the dark). Next day took it apart. The magnets had completely disintegrated into lumps of magnetic goo deposited around the compass card. (Maybe polymer enclosed magnets, compass fluid dissolved the polymer?)
So far my emails to the company have been replied to with "it would be too expensive to send you a replacement card".
Shit, FedEx can send a small package around the globe for $20!! I pointed this out to the company a week or so ago, no subsequent response from them...........
(Bought a couple of rod magnets and busy epoxying the in place to repair it myself.)
More soon, I hope.........