CNN

Portland USA, Jun 22: While the movie version of The Da Vinci Code is fizzling out at the box-office, another da Vinci mystery is drawing record crowds in the US.

This time it is a painting in the Portland Museum of Art of Mona Lisa, which is not smiling.

There is no way to analyse when the painting was made, but some say the eyes have it. In this case, the key to unlocking the mystery of the two Mona Lisas could be the smile.

The original Mona Lisa, which hangs in the Louvre in Paris, is smiling. The Mona Lisa in Portland, Maine, is not.

"I think I like it better without the smile, strangely enough," a visitor Mos Bob Wickowski says.

The famous painting by Leonardo da Vinci has had a renaissance of sorts because of the blockbuster film The Da Vinci Code where she appears larger from on the left than on the right.

Playing on the popularity of the movie, the Portland Museum dusted off and put on display what it believes is an unfinished "study" of the Mona Lisa, painted by the master himself.

It bears a striking resemblance to the original and people are flocking to see it.

"I believe this is the real deal. It has that feeling," a visitor Cissie Lindeman says.

Some experts also agree. A Harvard University study concluded the Portland painting is of the same period as the original, but others believe that brush strokes show it was done by a left-handed artist like Leonardo.

It is believed that Leonardo da Vinci painted the Mona Lisa for a man who wanted a portrait of his wife.

"It is a sweeter painting, it is a gentler, more feminised celebration of a woman really at the height of her attractiveness. This is the girl you would take home to mom. The other woman is a mysterious creature," Director, Portland Museum of Art, Daniel O’Leary says.

Still many believe the Portland painting is nothing more than a fourth-rate copy.

"Well, I suppose there's a chance that it's an original as there's a chance that the moon is made of cheese," says an art history professor at Columbia University, James Beck.

Beck, an expert in Italian art, says the slight "smile" in the original is Leonardo's signature. He added that the hands in the artist painted so magnificently are not the same in the Portland version.

Beck also adds there is no way to analyse when the painting was made.