Rebuilding a Victor Talking Machines Exhibition Sound Box will dramatically improve the quality of the sound produced. The old rubber (flange and gasket) will likely have hardened or cracked, so the response will be weak. There's a good chance the beeswax seal (or SuperGlue) will have broken and the screw in the mica diaphragm will have loosened.
These Sound Boxes are easy to rebuild. You can order a kit from any good phonograph parts dealer; I like Ron Sitko, Antique Phonograph Parts & Service 518-371-8549 in NY, or George Vollema at http://www.victroladoctor.com I suggest you buy at least two kits for the Exhibition Reproducer or more correctly "Sound Box". These are also available on eBay, but some prices are crazy. The mica diaphragm usually does not need to be replaced.
Check out these easy instructions:
http://www.nipperhead.com/old/rep_exhib.htm
Good luck.
PhonoJack
http://www.PhonoJack.com