This piano vocal score appears with a number of different versions, differing in which singer’s photo is featured on the cover.  I believe all are rare, including this one, featuring the actress/singer Dorothy Lamour.  This sheet music is in outstanding condition with no tears or other issues.  There is a name inscribed on the front and back covers.  

"A Sailboat in the Moonlight" is a 1937 composition by Carmen Lombardo and John Jacob Loeb.

Carmen Lombardo (July 16, 1903 – April 17, 1971) was lead saxophonist and featured vocalist for his brother Guy Lombardo's orchestra. He was also a successful composer. In 1927, Carmen Lombardo was the vocalist of the hit record Charmaine, performed by Guy Lombardo and His Royal Canadians.

John Jacob Loeb (1910 – 2 March 1970) was an American composer. He wrote music and lyrics for many popular songs, such as "Rosie the Riveter" (1942), "Seems Like Old Times" (1945), "Masquerade", "Reflections in the Water", "Sweetie Pie", "Boo Hoo", "A Sailboat in the Moonlight" and "The Maharajah of Magador".

Dorothy Lamour (1914 - 1996) was an American actress and singer who appeared in more than 60 films. She is best known for her roles in the Road to movies, a series of seven comedies starring Bing Crosby and Bob Hope that ran from 1940 to 1962. 

Lamour was born Mary Leta Dorothy Slaton in New Orleans, Louisiana on December 10, 1914. She began her career in the 1930s as a big band singer, and in 1936 she moved to Hollywood and signed with Paramount Pictures. She has also appeared in Disputed Passage (1939), Dixie (1943), On Our Merry Way (1948), Johnny Apollo (1940), and A Medal for Benny (1945).