There were two Kassite kings named Kadashman-Enlil. The first reigned circa 1375-1360 B.C., the second circa 1264-1255 B.C..
Kadashman-Enlil I was a contemporary of Akhenaten and is known to have corresponded with the Egyptian king. Three letters from Kadashman-Enlil I can be found in the Amarna Letters, a group of clay tablets found at Amarna and all written in Akkadian - the diplomatic language of the period.
The inscription on the above seal is extremely fine and rare, naming the King himself. Written in an highly artificial language, the last two lines of the text are difficult to interpret.