Kaja Veilleux has been hunting New England attic treasures for more than 50 years. He once found a copy of the Declaration of Independence sitting on a pile of trash, and he made headlines this year when he stumbled upon a million-dollar portrait gathering dust in an old farmhouse in Maine that may have been painted by the Dutch master Rembrandt Harmenszoon van Rijn.Video above: Veilleux hunts for New England attic treasures, helps people sort gems from junkThen there was the time, Veilleux said, he was shown a $50,000 gold coin kicking around in a tool drawer, only to have the well-meaning owner destroy much of its value before he could auction it by using a scouring pad to clean it — and scratch it.”It’s like a treasure hunt every day,” Veilleux said with a chuckle.Many people dream of cashing in on some dusty, old heirloom. In October, three sisters …