Yes, 1955. Most of you were very close and congrats to Val and Lauriana who guessed the year correctly!
Tom Brigance was a well known designer of American sportswear. He worked in London for Jaeger before coming to New York in 1939 as the in-house designer for Lord & Taylor. He was noted for his use of soft draping, unusual fabrics, and interesting prints. He was absent from the design world from 1942-47 while he served in the war. Upon his return, he once again designed for Lord & Taylor, until he announced his resignation in March of 1949 to join Charles Nudelman. He didn't stay long, however, as by 1951, Brigance was the exclusive designer at Frank Gallant. In the 1950s, 60s and 70s Brigance designed for several manufacturers including Sportsmaker, Gabar and Sinclair as well as under his own name. He retired in the late 1970s and died on October 14, 1990.
The cute playsuit shown above was designed under Brigance's own label in 1955. This is actually two pieces: a short play dress with matching bloomers made of Mooreville cotton plaid. This would have been worn on the beach, by the pool, or perhaps for boating. It was far too short to go into town in 1955! Note how the bottom two buttons of the dress are left daringly unbuttoned for the photo. The ad calls this a "Miniature dress." Sold for $25 in 1955 (about $211 in today's dollar.)