The family crest of David Dunbar Buick was not officially used until the 1937 model year. There were times in the 1930s-40s that Oldsmobile and Chevrolet used similar badges.

From 1903-1936 most badging included a blue rectangle with the word "Buick" in a diagonal script. Included often were the words "VALVE IN HEAD" in the upper left part of the rectangle, and "MOTOR CARS" in the lower right. The Valve in Head subtitle refers to its overhead valve engine.

The Buick shield logo was widened to fit more properly with the postwar designs that featured wider grilles.

Beginning in 1959, the logo split into three, to signify the all-new series names Le Sabre, Invicta, and Electra (and Electra 225) which replaced the familiar Special, Century, Roadmaster, and Limited names. For 1959, in some literature, these were represented by three diamonds in the colors red, yellow, and blue (see attachment). For the most part, the tri-shield set inside a ring appeared on models of 1960 to the present. An eagle (named "Happy" was used with the letters Buick on some models from 1975 through the 1980s. It should be noted that the red, white, and blue coloring and the interior detail or the tri-shield logo is no longer present.
References:
http://www.cartype.com/page.cfm?id=270&alph=ALL
http://www.buickheritagealliance.org/buickhistory.php
http://dixitcomunicacion.wordpress.com/2008/02/19/evolucion-de-los-logos-de-automoviles/
Attachment: 1959 Buick promotional matchbook