Like so much of US Girl Scout history, the story of troop crests begins in Great Britain. When Juliette Low brought the idea of Girl Scouting to Savannah, she brought along the tradition of patrol crests. Instead of numbers, each patrol chose the name of a flower, tree, shrug, or bird as its symbol. The first four crests used were the white rose, the carnation, the red rose, and the poppy.
The first crests were designed by a Miss Farmer, the art teacher at Pape School in Savannah. In 1913, Juliette brought back some Girl Guiding crests to be used in Georgia. These original crests were round and black, with edges embroidered in red. These original crests were worn on the sleeve but placement soon switched to the area over the left breast pocket.
These crests were replaced by 1914 with an oval design and the color was changed from black to khaki with a black border in 1918 and blank crests were made available for troops wishing to choose their own design. This option was popular in the early years of scouting, even though mass-manufactured crests were available. The color of the crests changed to a gray-green in 1928, and since 1930 the color is generally changed to match the choices in colors for the official uniforms. Check out this link to view some of these older versions. http://www.vintagegirlscout.com/trpcrests.html
At one point in the 1920s, there were over 40 troop crests. Some of the earlier troop crests used included the cornflower, the nasturtium, the fuschia, and the thistle (all discontinued in 1952), the pink carnation, the cardinal flower, the clover, the goldenrod, the holly, the jonquil, the iris, the meadowlark, the oak, the sunflower, the scarlet pimpernel, and the crocus, (all discontinued in 1984), and the blue bell, the brown pansy, the blue bonnet, the buttercup, the mountain laurel, the pine cone, the poppy, the robin, and the daisy (all discontinued in 1989). In 2010, the set of 23 that had been in use were discontinued in their entirety and a new set of 16 was issued. The new set of crests have been changed from an oval to a shield shape. There are 16 choices, and, if none of these seems to fit, troop also may design their own.
Troop crests were generally selected at the end of Brownies, but the new crests indicate that they are for Daisies through Ambassadors. Troops should select a crest that represents their identity, and I think that identity cannot possible emerge as early as first grade. There is no harm in waiting until Juniors to make this selection. Troop crests should be chosen carefully because traditionally, once chosen, the crest never changes for a troop. Crests are worn on the right-hand side of the vest or the upper part of the sash centered just above the troop numbers.