The baseplate or protractor compass
This type of compass was invented by the Kjellstrom 
brothers
during the World War II era and consists of a rectangular baseplate, which
is marked with a red arrow pointing along the long axis, and a rotating
compass housing marked in degrees (360 degrees for the full circle in most
of the world, but 400 on some European compasses). Marked on the floor of
the rotating compass housing are an arrow and a set of lines parallel to
that arrow. Additional features may include a lanyard for attaching the
compa ss to the wrist, scale bars for measuring map distances along one
or more edges of the baseplate, a magnifying glass for reading fine map
detail, and templates of a circle and triangle for marking orienteering
courses on the map.