My father worked in Edinburgh’s North British Rubber Company 80 in 1947-1948, when it was probably the Scottish capital’s largest factory. The testimonial shows he had been employed by the company from March 1947 to September 1948.
It is not unthinkable that my father established contacts in Burma that eventually enabled him to later work for the North British Rubber Company in 1947-1948. However, after a brief search on the Internet, I could not find any connections between the company and Burma. On the other hand, I did learn some interesting facts about the company; they supply the Queen with her favourite footwear, ‘wellies’, or ‘Hunter wellingtons’.81
Wellington Boots

The company was responsible for famous inventions such as the rubber Wellington boot, amongst other things. The Wellington boot was originally a type of leather boot adapted from military-style riding boots.
They were worn and popularised by the 1st Duke of Wellington, thus the name of the boot.
The ‘Wellington’ boot became a staple of practical footwear for the British aristocracy and middle class in the early 19th century. Arthur Wellesley, 1st Duke of Wellington (1769–1852), was one of the leading military and political figures of 19th-century Britain. He is among the commanders who won and ended the Napoleonic Wars when the coalition defeated Napoleon at the Battle of Waterloo in 1815.82
Royal Family

The British royal family members are often seen wearing ‘wellies’. Perhaps this is an implicit act of patriotism—or maybe they just like to present themselves as ‘country people’, and not ‘above’ the ‘ordinary’ people.
80 Partly adapted from the Edinburgh Evening News, article by David Hepburn Monday, 28th February 2022. https://www.edinburghnews.scotsman.com/heritage-and-retro/heritage/17-pictures-from-the-1950s-and-1960s-of-edinburghs-north-british-rubber-factory-359013
81 https://www.homesandgardens.com/news/princess-diana-black-friday-hunter-boots
82 Adapted from the following website: https://en.wikipedia.org/wiki/Arthur_Wellesley,_1st_Duke_of_Wellington