Calling my Asian Readers

I am trying to identify a marble Chop or seal with the following imprint.

Can anyone identify what this is and what its purpose or meaning is?

I am assuming it originates from Asia somewhere  and that it may be an official stamp of some kind but I do not recognise the characters.  If you can help please add a comment to this blog posting.

We are off to Paris for a few days so will not know if someone has come up trumps until the end of the week.