Mystery Art Pottery Vase

Hello,
     This piece has been a constant puzzle to me. It has the look of many of the well known art pottery companies but there isn't any known marks or labels on it. Most art pottery is well documented shape and style wise. The only marks are the three lines or maybe roman numerals on the bottom. It stands 10 1/2" tall and the top is 6" in diameter with a smooth matte green finish. Any thoughts ??

                                                                                                               Thanks for any help or expertise,
                                                                                                                             -Mike-