Our ranges of super durable, tarnish-free instruments have been coated with a newly developed protective coating using advanced surface treatment technology. This coating, far superior to lacquers and varnishes, can withstand more than 720 hours (the longest test period for this process) under NSS (Neutral Sea Salt) laboratory testing. NSS testing is a certificated and standardised test method used to check corrosion resistance of coatings on metals such as brass, zinc and steel. It is an accelerated corrosion test that produces a corrosive attack on the product coating from which the results can predict its suitability for use as a protective finish. These instruments will resist tarnishing even when exposed to the harsh marine environment for extended periods. Our "Chatham" range have Brass cases with super durable, tarnish-free coating and QuickFix fitting system. This unique QuickFix system allows the instrument to be locked hard to a bulkhead or wall but removed, in seconds, by hand. The instrument is supplied with a case plate which is screwed to the wall or bulkhead (instructions and drill hole template included). The instrument then simply slots over the base plate and with a gentle twist, is locked on. A reverse twist removes it again. This makes changing batteries easy, removal for storage easy, and avoids the tricky job of not scratching your polished case when screwing the instrument to the wall! QuickFix can also act to seal the instrument mechanism making it waterproof. In underwater tests, clocks fitted with the QuickFix waterproof system worked continuously at a depth of 300mm for more than 3 months. Note: barometers with the QuickFix system do not have the full waterproof system as these instruments need exposure to air pressure in order to operate. Case diameter 7", face diameter 5", depth 1.5". Quartz clock movements use one AA battery.