  We have observed a sample of OH 1612-MHz masing objects in all four OH
ground--state transitions with the Australia Telescope Compact Array. One
likely post-AGB object is found to emit in the 1612-MHz, 1665-MHz and 1720-MHz
transitions. We discuss the evidence that this object may be an early post-AGB
object and the possibility for such a circumstellar envelope to harbour a
1720-MHz maser. We argue that during a very brief period, just after the star
has left the thermally-pulsing phase of the AGB and the wind velocity starts to
increase, post-AGB objects might show \sath emission. The best objects to
search for such emission would be those that are masing at 1612 MHz and 1665
MHz, but not at 1667 MHz nor in the 22-GHz H2O transition.
