Vintage postcard sized piece of MacMaster Island, situated in Passamaquoddy Bay near L'Etete and Little L'Etete Passages and St. Andrews, New Brunswick, Canada. The card was printed by Stanford's Geographical Establishment, London.
There's nothing printed or written on the reverse.
Someone appears to have typewritten over whatever was the original Letter A entry and substituted Willingdon Harbour, on the Little L'Etete Passage side.
Willingdon Harbour may have been named for Freeman Freeman-Thomas, Viscount Willingdon, who was the Governor General of Canada from 1931 to 1936.