The artwork, which adorns the then-Princess Elizabeth's handwritten note to Beatrice Stillman, the head housemaid at Royal Lodge in Windsor, features illustrations of dogs, horses and children.
The late monarch, who was around 10 years old when she wrote the letter, asks if "the birds are well, and the goldfish haven't died" when she was on holiday in Cornwall.
The note – which is expected to sell for £4000 ($A7600) – makes reference to primroses that the future Queen had picked, which she requests be shared amongst staff at Royal Lodge.
It also references "Jock", believed to be one of her ponies, as well as her nanny at the time – who auctioneers believe was Marion Crawford.
The letter reads: "Dear Beatrice, I am sending you some primroses we picked, wild. There are some pale pink ones as well as the yellow. It is very lovely here. We can go down on to the beach from the garden.
"I hope the birds are well, and the goldfish haven't died. Will you please give Cootie (Miss Coote I mean) and Mrs Wade some of the primroses to share. Jock is very well and happy here. Nanny and Joanna send their love to you.
"Love from Elizabeth."
The drawings on the letter were uncovered by Stillman's great-nephew William Westacott and include a pair of horses and highwaymen, a girl called Mary, a dog named Jim and a boy called John.
The letter was part of a cache of correspondence that Stillman kept after she was taken on by the Royal Family and will be up for sale at Hansons Auctioneers in Kent on February 27.
The collection also includes an undated written request from Elizabeth's younger sister Princess Margaret, which reads: "Beatrice! Please could you look after my bathing suit? Margaret."
Auctioneer Justin Matthews said: "When I first saw the letter, it gave me goosebumps.
"Queen Elizabeth II, as we remember her – with her love of dogs and horses – is astoundingly evident in this letter penned by her younger self.
"From these few lines we understand everything we later know about the late Queen. She is seen to be observant, kind and concerned with others' wellbeing, just as she was in later years.
"While Princess Elizabeth's concerns are all about her pets and the welfare of staff, Princess Margaret's are slightly more sartorial. Both seem rather fitting for the women they grew up to be."
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