With regard to the ruggedness of the Bosch MIC cameras........ they are extremely rugged. They are made from Billet aluminium and the head shell is almost an inch thick ! The 'cap' slides onto the head with such precision you can hear the air being pushed out before the O ring seal is reached. Once fully down into the head, the cap is hard to remove.
The faceplate is a vulnerability as it is a flat plate with O ring seals and relatively thin glass/Germanium windows. To break such you would need a hammer though. The seals around the head pivots are what you would expect to find on a mini submersible and are of Stainless steel with O ring pivot seals.
During testing the cameras are vacuum tested for leaks and full submersed in a water bath. They are rated as submersible but I cannot recall the depth rating or duration.
Any ruggedised enclosure can fail in service. Paint coatings can be breached allowing corrosion to form underneath and O ring seals can age or fail. Like any high performance ruggedised product, they all need some level of condition monitoring and maintenance to ensure the longevity of the service life. Military tanks, weapons and deep sea submersibles all need maintenance and inspection.
Any MIC that is in a terrible state of corrosion or that has suffered seal failure has not been monitored or maintained. Such is not uncommon in 'set and forget' situations where casual access to the camera after installation is very difficult or dangerous. Oil Platforms are often an example of such decisions. The camera is used until it fails or degrades and is then replaced as part of a major maintenance uplift. The value of the Camera is depreciated over it predicted life of approx 10 years and then it becomes scrap.
I do not know the history of your cameras but the fact that the camera modules still work suggests that at least the head seals did not fail completely as water inside the head globe would damage the thermal camera optics quite quickly.
Sadly equipment that is ruggedised is exposed to very harsh working conditions and so used examples can be in very battered condition.
One of my MIC412's was standard fitment on our armoured fighting plarforms in Iraq, so the 412 is rugged enough for Military deployment on armoured vehicles. That says a lot for its design.
The down side of the 412 is its size and weight. Small and light it is not ! This may explain their low value on the secondary market. I paid £400 for one.
The thermal camera module is not the usual compact FLIR Photon mini camera module that we often see inside CCTV housings etc. It is an open chassis design that would need to be placed inside some protection for use outside the 412. I assume the chassis was used as the heavy duty head casing provides all the required dust, moisture and impact protection.
The Photon is not a bad little camera though
Fraser