Sanders, who occasionally appraises items for PBS's Antiques Roadshow, often employs "the fine art of letting people down gently."
But on a recent Saturday while volunteering at a fundraiser for the small town museum in Sandy, Utah, just south of Salt Lake, Sanders got the surprise of a lifetime.
"Late in the afternoon, a man sat down and started unwrapping a book from a big plastic sack, informing me he had a really, really old book and he thought it might be worth some money," he said. "I kinda start, oh boy, I've heard this before."
Then he produced a tattered, partial copy of the 500-year-old Nuremberg Chronicle.
The German language edition printed by Anton Koberger and published in 1493 is a world history beginning in biblical times. It's considered to be one of the earliest and most lavishly illustrated books produced after Johannes Gutenberg invented the printing press and revolutionized publishing.
"I was just absolutely astounded. I was flabbergasted, particularly here in the interior West," Sanders said. "We might see a lot of rare Mormon books and other treasures, but you don't expect to see a five centuries old book, you don't expect to see one of the oldest printed books in the world pop up in Sandy, Utah."
The book's owner has declined to be identified, but Sanders said it was passed down to the man by his great uncle and had been just gathering dust in his attic for decades.
Because of the cotton bond paper it was printed on, not wood pulp paper like most present-day works, Sanders said the remaining pages have been well-preserved albeit literally coming apart at the seams
"Barring further calamity or disaster, it will last another 500 years," he said.
And Sanders is certain it's not a fake.
"It passes the smell test," he said. "I'm not sure there's ever been a forger born who is ambitious enough to hand-create a five centuries old book in a manner sufficient enough to fool people."
But what's it actually worth? Turns out, not much.
It is believed there are several hundred copies in circulation worldwide, making it not-so-rare of a find, and about two-thirds of its pages are missing.
Still, it's not the monetary value that excites Sanders.
"Just the opportunity to handle something from the very beginning of the printed word and the book itself, especially, ironically, in the 21st century with all this talk of the death of the book, and here we have a book that's survived 500-plus years," he said. "It's just exciting ... The value of an artifact like this to me is the least interesting part of it all."
Sanders is displaying the copy at his rare book shop in Salt Lake City.
San Francisco-based antiquities book dealer John Windle said if this copy of the Nuremberg Chronicle were in mint condition and fully intact, it could be worth up to a million dollars.
One in such shape sold last year at a London auction for about $850,000, Windle said, but not so much because it's such a rare find.
"The rarity of the book has almost nothing to do with its value," he said. "If you're collecting monuments of printing history, monuments of human history, if you're collecting achievements of the human spirit through the printed word, this is one of the foundation books ... Every book collector wants a copy of that book or at least some pages from it."
Windle noted that while its worth to collectors is priceless, it is "probably the most common book from the 15th century making its way onto the market these days."
"We have a saying in the book trade: there's nothing as common as a rare book," he added.
Because of this book's tattered state, Windle said it's likely worth less than $50,000.
"It basically kills the value," he said. "If it turned up in perfect condition in Salt Lake City, now that would be amazing. That would be astounding." Luise Poulton, curator and head of rare books at the University of Utah's J. Willard Marriott Library, called it "an exciting find," but largely just because of the way it surfaced.
"It's that classic story," said Poulton, who has several pages from another copy of a Nuremberg Chronicle on display. "You really never know what's in your attic."