This was once a very well known export brand in the United States, belonging to Taylor & Ferguson, who set up as blenders in 1931. They were acquired by Bloch Brothers (Distillers) Ltd., after the Second World War, the latter having also bought Scapa Distillery near Kirkwall in the Orkneys (and also owned Glen Scotia in Campbeltown from 1930). The whole shooting match was sold in 1954 to the Hiram Walker group, which had come to Scotland from Canada to establish what became a very substantial whisky business, only to sell out in 1987 to Allied Lyons. (Most of the Hiram Walker assets are now owned by Pernod Ricard).
It is not clear who originated the Ambassador brand - Taylor & Ferguson or Bloch Brothers. Here is a label from the 1940’s clearly showing it as Bloch Brothers and showing them as owners of Glen Scotia and Scapa distilleries. Taylor & Ferguson, under Hiram Walker, became the licensee of Scapa Distillery and the latter’s product featured strongly in the Ambassador blend. It was promoted as ‘Scotch at its World’s Lightest’, and Ambassador continued to be available, as Deluxe, Deluxe 8 and 12 years old, and Royal 12 and 25 years old, principally in the US, until the late 1980s. Bloch Brothers was dissolved in 2010 and Taylor & Ferguson the following year.