In response to John Wolff's note in MMDigest 980505:

My Aeolian Celestina pneumatics are equipped with an _external_ hinge.
The pneumatics were recovered with the two wooden sides parallel and
the typical overlapping joint on one end.  After this was completed,
_both_ ends and the sides of the pneumatic were creased (in typical
pneumatic fashion) and the pneumatic collapsed.  Then the end with the
joint was permanently held closed by gluing a small strip of pneumatic
cloth across from top to bottom boards, thus forming the external
hinge.

Paul DeWitt