That is, until Swann's New York autographs auction, whose results were published today (November 12).
The star lot was a letter written by the former second-ever President of the United States to Governor of NH William Plumer (addressed as "Respected Sir"). In the letter, Adams writes of sending his grandsons to England, and wonders what the future holds for him there.
"I am, this week embarking two grandsons to meet their parents in England. They go for Liverpool in the new Packet, Captain Bronson," writes John Adams.
"How my son will terminate his career, or how any other man in public service in this country will come out at last, no intelligence short of divine wisdom, I believe, can foretell."
A similar lack of divine wisdom among Swann's autographs appraisers led to a pleasant surprise at the New York sale. Swann's experts didn't foretell that Adams' letter would sell for $24,000 - nearly doubling its $15,000 pre-sale estimated value.
The letter's success at auction is likely down to its personal content: a heartfelt confession by a man of immense historical status and renown.
For instance, he also writes of his son (an ambassador): "It is probable he will lose in England, as his father did, all the little popularity he ever had.
"And the sincere wish of my heart is, that he may return to his country and enjoy in private life as much tranquillity and comfort as his father has done for the last fourteen years."
This is all the more impressive considering that his son happened to be John Quincy Adams, whose popularity didn't dwindle sufficiently to prevent him from later being elected sixth President of the United States. His term began in 1825.
The framed letter is dated April 11, 1815 - almost a decade and a half after Adams's 1797-1801 presidency - with a few short closed tears repaired with a tissue verso, apparently with "minor scattered soiling".
And this isn't the first time that a confessional letter by Adams has proved a hit at auction. A letter written by the influential Founding Father in response to a colleague in 1819 was auctioned by Heritage Auction Galleries, also in New York, for $160,000 in February.
In the letter, Adams writes of his impressions of the national mood in the United States when he was sworn in as President.
Compared to the hundreds-of-thousands realised by the 1819 Heritage, it appears that the lucky buyer at Swann netted themselves a (relative) bargain - and a bona fide piece of history whose value is sure to appreciate in future years.
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