Skeleton [Bit or Warded] Keys

Solid-barrel brass keys, many of which were made by hand, look great and worked hard in old homes and early retail spaces. 

Bit keys were used in hotel and institutional applications, in some cases, as late as the 1970s.

These are local examples from a sanitarium, parts of which still define the village of Clifton Springs, New York.

Bit keys may fold for one of two reasons; they're too big (left) or they operate and remain in pocket door locks (right).

Known to many as Steamship Keys, these long, heavy brass keys are often adorned with brass tags or embossed or punched numbers and letters. 

Stout brass and steel keys were (and are) often used for railroad switchgear, and signal/communications boxes.