This is Addy's Birthday Outfit. American Girl retired this set in 2013. It is brand new and increasingly rare.
American Girl described it as follows. The day Addy chose as her birthday was a special one, and so was the outfit she wore to celebrate! Dress Addy up in her best ecru blouse with double puffed sleeves, rickrack trim, and a trio of tiny buttons. Add the chocolate-and-cream-checked pinafore and fancy knit stockings.
For a finishing touch, tuck her hair back in a fashionable snood trimmed with a satin ribbon and two faux yellow feathers, compliments of Sunny!