An original Norman Rockwell painting owned by a high school in central Massachusetts is heading to auction after it hung for decades in the principal's office.

“Willie Gillis in Convoy,” depicting a group of soldiers riding in the back of a military truck, is just coming to light from storage in the Gardner, Mass., high school. A charcoal study of the scene was included in the artist’s catalogue, but the finished painting has been in obscurity until now.

The story behind the painting is that it was gift sixty years ago to Gardner High’s principal, F. Earl Williams, from the artist himself. Williams was supposedly at Rockwell's Vermont studio looking to buy a painting for a graduating class. Rockwell said he probably couldn't afford his work, but ended up giving the painting to the principal.

The painting was put in storage in 2001 for security reasons. Gardner Mayor Mark Hawke said he decided it was time to sell the painting last fall when Rockwell's "Saying Grace" sold for a record $46 million. It goes under the hammer at Sotheby's on May 21 with an estimate of $1.5 million to $2.5 million. Proceeds of the sale will benefit the town of Gardner.

Principal Williams reportedly bought other art for the school including works by Marguerite S. Pearson and Harrison Cady.