The 13-cent Montana State Flag issue (Scott 1673) depicts the modification of an 1898 flag design by Colonel Kessler, head of the First Montana Infantry, which was adopted by Montana's Legislative Assembly in 1905. The rectangular banner pictures the state seal centered on a blue field.
The state flag is blue with a gold fringe on the top and bottom edges. The Montana state seal depicts a brilliant sun over snowy mountains, forests, and cliffs. The Great Falls of the Missouri River serve as the background for a pick, shovel, and plow. These tools represent Montana's mining and farming economies. A ribbon at the seal's bottom bears the state motto—"ORO Y PLATA" (Spanish for “Gold and Silver”).
In 1981 the Legislature passed a bill requiring that the word "MONTANA," printed in Roman letters, be positioned above the seal. This was changed to a 'Helvetica' bold font in 1985.
Scott 2005 Specialized Catalogue of U.S. Stamps and Covers
SHG Resources (http://www.shgresources.com/mt/symbols/flag/)