John Dopyera developed the resonator that made National famous. National was formed in 1925 with George Beauchamp, and Dopyera's brothers. They started making banjos and guitars. In 1928 their first mandolins emerged on the market. The mandolins were similar in style to their guitar counterparts.
National ran into financial issues as well as many other internal problems during the 1930s. In the mid 1930s, National merged with Dopyera's new company, Dobro. In 1936, National/Dobro moved to Chicago, Il. Mandolin production ceased in 1940, and never started again. National was reorganized in 1943, as the company "VALCO." Valco lasted until 1967, when Kay bought out Valco, but Kay/Valco went under themselves in 1968/69.
A few instruments have appeared with National and Valco on them that were made in Japan, but no mandolins have shown up. Information courtesy Bob Brozman, The History and Artistry of National Resonator Instruments.
Mandolins previously produced in Los Angeles, CA between the mid-1920s and the mid-1930s and in Chicago, IL between the mid-1930s and 1969.

NATIONAL Mandolins Models

NATIONAL Style 0 Image

NATIONAL Style 0

- full-metal body, single-cone resonator, maple neck, celluloid binding, ebony fingerboard with dot inlay, four-per-side tuners, chrome hardware, polished body with Hawaiian design, mfg. 1931-1940.

NATIONAL Style 1 Image

NATIONAL Style 1

- German silver metal body, tri-cone resonator, maple neck, celluloid binding, 12/18 fret ebony fingerboard with dot inlay, four-per-side tuners, chrome hardware, plain polished body with no engraving, mfg. 1928-1940.

NATIONAL Style 2 Image

NATIONAL Style 2

- German silver metal body, tri-cone resonator, maple neck, celluloid binding, 12/18 fret ebony fingerboard with dot inlay, four-per-side tuners, chrome hardware, polished body with Wild Rose engraving, mfg. 1928-1936.

NATIONAL Style 3 Image

NATIONAL Style 3

- German silver metal body, tri-cone resonator, maple neck, celluloid binding, 12/18 fret ebony fingerboard with dot inlay, four-per-side tuners, chrome hardware, polished body with Lily of the Valley engraving, mfg. 1928-1936.

NATIONAL Style 97 Image

NATIONAL Style 97

- nickel plated brass body, tri-cone resonator, mahogany neck, celluloid binding, 12/18 fret ebony fingerboard with dot inlay, four-per-side tuners, chrome hardware, polished body sandblasted scene of a female surfer, colored with airbrushe...

NATIONAL Triolian Image

NATIONAL Triolian

- wooden body, single-cone resonator, four-per-side tuners, chrome hardware, Light Green finish with a light overspray of several colors, early models feature a bouquet design and others have a hula girl Hawaiian design, mfg. 1928-1940.