I'm not sure about the ID. There was "problems" about this taxon (after 2004, the former "Stan impressa" was renamed as Stan gibbosa; and the former "Stan gibbosa" was renamed as Stan confusa)
For me it is a gibbosa, 'cause in the old descriptions of the "impressa" (today a nomen nudum) there was cited the "eyes" not only in the hipochile, but also in the petals (you can see the "eyes" in the petals in some pics)