Note
http://www.antiqueradios.org/gazette/SWevol.htm
QST Oct 1931, p. 2.
Radio News, Jun 1932, p. 1062.
QST, Oct 1932, p. 68.
Lafayette catalog number 55, p. 68.
Radio News, Jul 1933, p. 51.
QST, Sep 1933, p. 59 (available with 2.5 volt AC tubes, 6 volt AC/DC, and 2
volt dry cell tubes)
QST Oct 1933, p. 74. "New and Improved"
Radio News, Jan 1934. p. 437.
Radio News, Jun 1934, p. 762. (now available in AC, DC, and 2 volt battery versions)
QST, Oct 1937, p. 55. (A few notes)
Lafayette catalog number 78, p. 146.
QST, Feb 1941, p. 59. (First major change)
QST, Jan 1965, p. 10. (a reference to SW3 in 1931)
Sometimes appeared in catalogs with model numbers like these:
ACSW-3, AC operation
6DCSW-3, 6 volt DC
2DCSW-3, 2 volt DC
National designed the SW-3 for the Great Depression market. Its circuit was similar to that of the SW-5, but lacked that model's push-pull audio output stage. It was eliminated in an effort to keep the selling price low enough to attract customers when it was introduced in 1931. The three-tube regenerative set was still capable of good performance and remained part of National's product line for more than 15 years.
References
Technical description. QST, Sep 1931, p. 9
Convert to superhet. Radio, Apr 1934, p. 12.
Brief description. Radio News, Jun 1934, p. 762.
Convert to superhet. Radio, Mar 1936, p. 38.
