This is an interesting item, truly, but it is not a keris.
The figure is Semar. To do justice to an explanation of Semar would require many more words than could be justified in a forum dealing with the keris. Here is a short, simple explanation that does not even come close to providing an understanding of Semar, but it is an easy place to start.
Semar is The Soul of Jawa, and a very popular talismanic icon.
The hilt probably is agate, in the Mangkunegaraan in Solo there is a display of small daggers with agate hilts that are believed to have been in the possession of female abdi dalem (court attendants). Solo has a long history in lapidary work, and polished stones are very popular in Central Jawa.
I would be inclined to attribute this piece to Solo, late Colonial era.