This is a "Corona Three Special," or folding typewriter. The "special" indicates it is a colored machine, rather than black. It was considered portable -- the carriage folds over on top of the keyboard, so it will fit into a very small case. The "three" indicates there are three rows of keys on the keyboard. This machine is likely from the 1920s.

(Courtesy of Lowell Plum)

Lowell Plum repairs typewriters for Arrow Office Products in Boulder. He says that many teenagers are fascinated with the machines. Some businesses also find them handy -- like car dealerships and realtors. Plum spoke with Colorado Matters host Ryan Warner. 

The "Mercantile" is a rare, vintage typewriter from the early 1900s. Lowell Plum is repairing one at Arrow Office Products in Boulder, Colorado.

(Courtesy of Lowell Plum)