  We study the dynamics of a spherically symmetric dust shell separating two
spacetime domains, the 'interior' one being a part of the de Sitter spacetime
and the exterior one having the 'extremal' Reissner-Nordstroem geometry.
Extending the ideas of previous works on the subject, we show that the it is
possible to determine the (metastable) WKB quantum states of this gravitational
system.
