May Day after Maurice Prendergast

This is one of the paintings from my collection that could be the real deal, but I've never tried to confirm it. I found this in a thrift shop so covered in dust that it was hard to see the image. It is very well framed and the back is sealed using heavy backing paper which I have never opened. It is after "May Day, Central Park" by Maurice Prendergast and is a 14.5" x 19.5" watercolor (opening of the mat). I was not familiar with this work at the time that I acquired it. It is on my art collection web site and a couple of people tried to buy it in very circuitous ways before a viewer noted that it was similar, but not exact, to the version in the Cleveland Museum of Art and that Prendergast was known for painting several versions of his paintings and there are several versions of May Day. Even if really his work, the value would not be enough for me to buy that private island, so I've never tried to have it examined.