Sir Ralph Champneys Williams was presented with a walking stick by Edward VII in the early 1900s, but that stick was destroyed in a fire.
Later, Sir Ralph's son wrote to King George VI to ask for a replacement, and the monarch sent him another stick which had belonged to Edward VII.
Despite its low value, auctioneers said the stick's story was "heart-warming".
Sir Ralph, born in Llanddeiniolen, was a former acting governor of Barbados, and he met King Edward VII and Queen Mary at the start of the 20th Century. The King presented him with one of his walking sticks, and the stick accompanied Sir Ralph wherever he was posted.
However, years later the stick was destroyed in a fire at his son's house in Kenya.
Sir Ralph's son, Major Geoffrey Howard-Williams, wrote to the then King, George VI, to ask for a replacement.
A letter from the King's personal secretary was sent from Sandringham, dated 29 December 1945.
It read: "I write to acknowledge the receipt of your letter of 31st October.
"Under separate cover I am forwarding you, by direction of the King, a walking stick which belonged to King Edward VII to replace the one which you had the misfortune to lose when your house burnt down.
"It has taken a little time to find this stick, which accounts for the delay, but His Majesty hopes that it may prove a suitable substitute."
The replacement stick - which bears the stamp "Balmoral" and Edward VII's crest - remained in the family.
Sir Ralph's great-grandson, the present owner, discovered it when he was clearing his late father's home in Devon.
It will be auctioned, along with the letter that accompanied it, on 27 February.
Auctioneer Duncan Chilcott said: "Obviously this walking stick - like the one it replaced - was a dear friend to Sir Ralph and while it is likely to sell for less than £300 the story behind how it came to be sent from Sandringham to Kenya is really heart-warming.
"Clearly Sir Ralph was held in very high regard by the Royal Family and it is a mark of King George's generosity, for which he was well known.
*I disagree with the auctioneer’s valuation. I predict that it will go a good bit higher.