It looks very much like the species rather than a cultivar. I know Minerva was one of D Engolf's Goddess series and they were released in 1986, That ROS had much fuller petals with no real discernible spaces between them. When we moved to Louisiana in 1956, there was a purple ROS beside the house we moved into. The previous owner told my Mom that it was a hibiscus called a Rose of Sharon. It looked very much like your picture. This is a pic of Minerva.
http://www.missouribotanicalga...
