Following are photos of my put-together 1858 doorbell although none of it is original so I don't know if this is helpful to anyone.
The knob is from a Victorian screen door. Not sure what the cast iron 'escutcheon' is from

Inside view showing a bell purchased on ebay & a pivot cover (my terminology) also from ebay:








Hole in the floor for wire to a missing basement bell:



I'm having trouble with photobucket so will post photos of the original hardware ASAP.

From what I've seen (mainly on ebay), there were several types of knob assemblies that went through the wall but I don't have any of those; something with a spring would have been useful but they rarely turn up & when they do, they're expensive. My basic setup is:
Knob + spindle w/screw hole + wire connecting spindle to bottom part of pivot

This post was edited by antiquesilver on Sat, Feb 23, 13 at 23:14

Other than a patched 1/2" hole on the outside, the following are the only clues that I inherited. The cast brass 'pivot cover' is larger & more substantial than the one I bought on ebay but the original pivot has been broken off making it unusable. This was mortised in to make it flush with surrounding woodwork & was in place when we bought the property.

The pivot with the iron weight/balance/? was found with plaster rubble in a small basement room directly below the front door. I had always thought it came out of the ceiling but on reflection it seems more likely that it was attached directly to a bell on the basement wall (probably just beneath the ceiling) with the other end wired thru the floor up to the main pivot/pull. When the outside pull was activated, both bells would have rung.

Following is a link I found online of a complete antique system. Much better photos & explanation than mine.

Here is a link that might be useful: Complete Bell System