In the watch industry there are mainly 5 types of materials that a case of a watch can be made of. 1. Precious metal – gold, silver or platinum 2. Titanium – very tough and light material but scratches easily 3. Stainless steel – various grades of stainless steel are available and can be plated with black metal or gold 4. Brass with plating- Almost always plated with gold or palladium and nickel in order to give it the color of gold or stainless steel respectively. 5. Alloy - a zinc die cast that needs also plating
John Harrison and the problem with GMT when at sea
Until the 17th century seamen had difficulty finding their coordinates at sea. They could easily find their latitude by measuring the angle between the Polaris (the North Star) and the horizon in the northern hemisphere and the Crux (or the Sothern Cross) and the horizon in the southern hemisphere. The measurement of latitude was found by measuring this angle. Measuring the angle was no problem with the invention of the sextant. A sextant allows for the measurement of an angle of a celestial object relative to the horizon.