Translation of "conscius" [sic] on stamp (Characters identified: 自覚的)
自觉的, just "self-conscious".

Note that, 覚 is seldom used today. It's an interchangeable character for 觉(simplified Chinese) or 覺(traditional Chinese), which means sense/feel.

PS: I think the one who made the stamp maybe didn't know Chinese. He or She might search conscius in an electronic dictionary and found the Chinese meaning 自觉的. However the translation can be greatly refined :)