A rare $500 bill from 1911 sold for the "bargain price" $322,000 US at a recent auction, the largest sum ever paid for a Canadian banknote.

The vintage bill, which features the image of Queen Mary, is one of only three bills known to exist, according to currency expert Troy MacDonald, who also served as an adviser to the man who purchased the vintage bill in the September auction in Long Beach, Calif.

"It is a very high denomination note from a very early period in Canadian history," MacDonald told CBC Radio's As It Happens on Tuesday.

"To have such a note with such a high value survive the Great Depression really makes it extremely special. Not a lot of people could afford to hold on to $500 in 1911 — it was a lot of money and only three from 1911 in the $500 denomination have survived."

MacDonald, who also operates the Moncton-based currency dealership The Monetary Man, said the bill was purchased by a Canadian real estate developer living in Dallas.

'It was definitely destined for the shredder and had it not dropped from the fold so to speak it was seconds from disaster.'—Troy MacDonald, The Monetary Man

The bill exceeded initial final bid estimates of $200,000-$300,000 set by the auction house Heritage Auction Galleries. But MacDonald said that while the final price broke Canadian records, it was nonetheless relatively modest.

"It went, quite seriously, at the bargain price of $322,000 US," he said. "That is a very conservative result comparative to other mature banknote markets."

The vintage bill was discovered serendipitously in Ontario, MacDonald said, noting it could have ended up in the garbage.

"My understanding is that a relative of someone who had passed away was cleaning out an office, going through the deceased's personal possessions and a pile of documents were in or on a desk," he said. The family's name and hometown are not known.

"It was definitely destined for the shredder and had it not dropped from the fold, so to speak, it was seconds from disaster."

The auction house described the bill as a "classic rarity" that had undergone only minor restoration.

"Its existence represents a true miracle of survival attesting to the fact that these high denomination pieces were actually used in commerce," the catalogue entry read. "If this were a United States issue, where this became only the third example known for the design type, it would easily be a million dollar note."