Your email address has been passed on to me from Joanne at Whisky.com, as I am responsible for the Buchanan's collection at Diageo's archive.

I would date the bottle to between 1955 and 1965. The Royal Warrant mentioned on the neck label of the bottle was granted by the current Queen in 1955, so the bottle must have been produced after this date. Additionally, the labelling on the bottles was not redesigned between this date and the mid 1960s, so it could be as late as 1965.

Hope this information is helpful.

Kind regards,

Alia