Lin had a prototype machine custom built by the Carl E. Krum Company, a small engineering-design consulting firm with an office in New York City. That multilingual typewriter was the size of a conventional office typewriter of the 1940s. It measured . The typefaces fit on a drum. A "magic eye" was mounted in the center of the keyboard which magnifies and allows the typist to review a selected character. Characters are selected by first pressing two keys to choose a desired character which is arranged according to a system Lin devised for his dictionary of the Chinese language. The selected Chinese character appeared in the magic eye for preview, the typist then pressed a "master" key, similar to today's computer function key. The typewriter could create 90,000 distinct characters using either one or two of six character-containing rollers, which in combination has 7000 full characters and 1,400 character radicals or partial characters.