I'm a printmaker doing etchings. Haven't done any serigraphs (silkscreen prints), but they are considered as multiple originals...because they are made by hand and not high-speed offset press. Each one is an original work of art, printed from several screens.
Is it signed and numbered Sandman? What is the edition size? Is it framed? Does the print have a border? (If border is cut down from the original size, the collectors value is greatly reduced.)
Modern serigraphs of a size 24' x 36" sell for around $300 to $350 top end locally....unless the artist is famous and commands higher prices. This is just a guesstimation.
In any event, if the print is signed and numbered, and is a serigraph, it is worth something moneywise, because it is an original artwork and not a reproduction.
It's possible a museum would be interested in it, if it's old and in good condition. I recommend showing it to your local museum curator for his opinion.
Never store the print in contact with cardboard, as the sulphuric acid in cardboard will damage the print. Use archive grade mat board or foam core to store it.
Good luck.
Les