Common Pocket Watch Case Types
Open face
The open face pocket watch has is the most common type found: the above example dating from the late 19th century. The bezel is opened by sliding your thumb nail in the gap at approximately one o'clock, there is usually a lip to aid opening. They can be quite stiff to open (I have broken many nails), so sometimes a knife placed in the slot and twisted slightly is a good method (of course being careful not to damage the case). The back cover is often opened with the top button. Depressing it releases a catch and the internal spring pushes the case open. Sometimes, a similar method to the bezel was adopted having a slight lip to slide your finger nail under.
Full Hunter
The full hunter pocket watch became most popular at the beginning of the 19th century, losing the glass and bezel in favour of a more robust front (pictured right). The bezel and glass were reintroduced and became popular. The front cover is operated by pressing the top button which releases a catch allowing the case spring to push the cover forward. The rear cover opens with a protruding lip.
Pair Cased
The pair cased pocket watch first introduced in C. 1630 was most c0mmon in the mid 18th century to early 19th century. However, there was a renaissance in the latter part of the 18th century (pictured right). The outer case was opened by depressing a button which released a clip allowing the two halves of the case to be separated. This revealed the winding arbour at the rear of the inner case, to set the hands the bezel was hinged at the 12 o'clock position opening at 6 o'clock.
Gun Metal ?
I often see watches being described as "gun metal" this seems to be a common mistake, they are in fact made of steel that has been through an oxidisation process, this process involves immersing the steel case parts in a caustic solution at about 180c, this gives the steel a small amount of resistance to rust and corrosion. Gunmetal, is in fact a type of bronze an alloy of copper, tin, and zinc.
Consular Cased
This is another watch description I often see made in error being being given to open faced watches, a consular cased watch has the appearance of a pair cased watch with high domed glass. However it is just a single case watch from France. Made in the Napoleonic era, and reputedly Napoleon's preferred case style hence the term Consul.