Whisky Glass Bottle Codes at the bottom How to date a bottle of Whisky Source: http://www.glassbottlemarks.com/bottlemarks/ (very useful site with a huge number of information)
Can't help with the codes, but they will be specific to the glass-maker and may or may not be translatable to a date.
George Ballantine originally operated from Edinburgh, but opened larger premises in Glasgow in 1865. He retired in 1881 and, although his two sons took over, the company name has remained “George Ballantine & Son”, although the labels are now branded “Ballantine’s”. However, since your bottle has the word “Ltd” after the company name, it’s later than 3rd November 1937, which is when they incorporated.
Incidentally, they redesigned their “Ballantine’s Finest” bottles to that ‘square’ profile during America’s prohibition era, allegedly to make it easier for salesmen to conceal them in their briefcases. They still use that profile today.
If you contact the company, they may be able to give you a more precise date: