China / before 2000
Safe-T 45762 Blackboard Compass
Safe-T 45762 Blackboard Compass
The Smithsonian catalogs Safe-T 45762 Blackboard Compass as compass in its Mathematics records.
WHY IT’S INTERESTING
This is an oversized form of the Safe-T Compass (1998.0033.03), for use at a blackboard or dry erase board. It is a white plastic wedge-shaped instrument, with a rotating clear plastic disc set inside the wide end of the wedge. Both long edges of the wedge have a row of 9 circular holes. The holes are marked for the radius of various circles, from 1" to 5". To draw a large circle, a marker or piec