Ancestor - Dewar's rare old scotch whisky

My grandad obtained 2 bottle's of Ancestor Dewar's rare old scotch whisky from a cellar of an old building in 1974 - drank one and keep one! The bottle is a square green bottle in pristine condition and still has the original wax seal on the dewar ribbon. It has no quantity shown and has 70 proof on the label. He is interested to find out any information on the bottle he kept.

If anyone has information they could provide, we would very grateful. There are 2 photos, one which shows the front and the condition of the bottle the other which shows a flip-top lid at the rear.

Happy to send photos's over in PM.

[Jojo]

Dewar's Ancestor was originally named Dewar's Ne Plus Ultra. The company's main deluxe brand from about 1907 onwards was Victoria Vat, however it wasn't Dewar’s only deluxe brand. Ne Plus Ultra was also introduced about this time, and was first registered as a trademark in 1909.

In 1954, Victoria Vat was re-named Ancestor, although Ne Plus Ultra continued to be sold in certain markets - but on a small scale.