The horn or "bell" was missing a section from the edge.
A mold was made of a "good" section of the rim and used to pour a section that was missing.
(see above)
 

The base had severe cracks that ran all the way through to the inside.
In some spots I'm not sure what was holding it together.
The cracks were stabilized by filling with epoxy that was made for metal.
The base was "distorted" at the cracks and had to be smoothed back down.
The entire base was spun on a lathe to smooth the epoxy and cracks.
A mold was made of a "good" section of the rim, and was used to pour a section of the rim that was missing.
(see photo above)

Results
 

Interior
The interior was much worse that the exterior.
The coil was "open" (had a break in the windings) and the armature was very rusted and could not be saved.
I only regret that I did not take any photos before I started work.
I was able to save the diaphragm section of the driver which was very large (about 3").
I used the interior of a USI military sound powered element to drive the diaphragm ("ear" element).
This element was left over from another restoration and it was missing a diaphragm, so it was a perfect match !!!
The upper part of the rod connecting them is from a RCA military sound powered element.

The results were that this horn can now work on a crystal radio because
it is much more efficient than the original Balanced Armature setup.
Not real loud in my area because of a lack of a very strong local station, but OK.
It also will work very well with a single tube battery radio such as a Westinghouse Aeriola Senior without an amplifier.

Compleated Horn