Prewar American Fyer seems to have suffered from "zinc pest" second only to Dorfan. Some of their old signals are really neat, but impossible to find in good condition, the castings are usually pretty crumbled. No one is reproducing these, either.
Fortunately, David Trickel is casting new replacements for the crumbled parts. They come as rough castings, and you have to spend some time drilling out the holes and cleaning up the castings with a burr grinder like a Dremel, and then painting. But it is well worth it. Also, because the Trickel castings are soft zinc alloy like the originals (although hopefully more stable!) they are easy to work with.
These guys like Trickel, and other parts suppliers, are doing a real service to the hobby: these would have just been junk otherwise.
Before and after:
