Estimated at $500-800, it sold for $870,000 (£583,890) - $1.09m with 25% premium added.
The 12½ x 10in (32 x 25cm) oil on board was catalogued as a '19th century Continental School Triple Portrait with Lady Fainting'. It suffered from cracks to the panel, paint loss, old varnish and had some restoration to the surface.
Nye said it had appeared so "remarkably unremarkable" that a number of Old Master dealers who saw it at the gallery during the viewing passed it up. However at least three telephone bidders, including the two Europeans who ended up battling it out, believed it had major significance.
The size, subject and figure types appeared to match Rembrandt's early series on the theme of the Five Senses which date from the mid 1620s.
Three works from the series are known - representing the senses of touch, sound and sight. This work, depicting a woman made unconscious through ammonia inhalants, would seem to represent smell.
The Senses series are believed by some, but not all, scholars to be Rembrandt's earliest surviving works.
On the day, the bidding started at $250 and, climbing over 200 increments, took around 15 minutes to sell.
At various points, the underbidder jumped from $210,000 to $300,000; then from $310,000 to $400,000 and again from $430,000 to $500,000.
After that point, the price went up in $10,000 bids until the auctioneer's gavel was knocked down to the anonymous buyer.