A pic of the same drawer from the underside shows the 'Quaker Lock' as described in the last post, but it's only when the two screws are removed:
...and the Cedar of Lebanon base is slid backwards can the first secret compartment be revealed, a 5mm space:
...between the two bases. Nothing very clever here, except some very careful routing of the stopped grooves in each of the sides to hold the trapped (veneered) base.
However, the second secret compartment is a lot more cunning....