The 78-year-old actor described how the discovery left his grandson both “astonished” and confused by the amount of things he had.
Michael wrote on his blog: “I emptied dark shelves and cupboards a long time ago, with the help of my grandson Wilbur, who is amazed that I have so much.
“I explain to him that I had over 70 years to accumulate it and that I have always been very bad at throwing things away.”
Among the most puzzling for the youngster were the two shoeboxes full of matchbooks, which the legend of the Monty Python had collected from “bars, restaurants and hotels around the world.”
Puzzled, her grandson asked, “Why, Grandpa? To which Michael replied, “Because as you get older you start to forget things. Your memory needs a boost and that’s what they give me.”
Michael shared a series of photos of his “Top 10 Bookmatch Memories” that represent the globe-trotter’s keen interest in travel. During his career he has featured a number of travel series for the BBC and traveled from the North Pole to the South Pole.
Beside each photo, he shared the short story behind, including where he found the matchbook and who he was with at the time.
The first find he included was closer to home, at a West Yorkshire restaurant he visited in 1984.
He wrote: “While filming A Private Function, we celebrated Alan Bennett’s 50th birthday here.
“A wonderful meal was only slightly spoiled by Maggie Smith discovering a piece of glass in her mixed salad.”
Another of his favorites was a book of matches he picked up on his first visit to the United States in 1972 with fellow Python Terry Jones.
Michael wrote: “We tried to see everything as fast as we could and Terry suggested we go down the Grand Canyon and back up in the morning. It wasn’t until going back up that he collapsed.
“Worst of all, the lodge where we found those matches ran out of beer.”
Terry died last year at the age of 77, four years after being diagnosed with rare and aggressive dementia.
Michael described him as “the spirit of the Monty Python”.