Hate to beat JoJo to the punch on this one, but your bottle actually dates to between 1967-1968.
In 1967 Buchanan's changed the labeling of their Black&White bottles, removing the Royal Warrant info
from the Shoulder-label, and incorporating it into the top of the Main-label with a Gold Coat of Arms.
In late-1968, the company discontinued the use of Spring-cap closures on Black&White bottles, in lieu
of modern Screw-caps.
Walter C Hurst