Rich,
I have not seen images that clearly show the construction of the hinge and have never had one of these in hand. Here are some additional images that may help you infer what the internal configurations might look like. I like the brass chargers best, especially the ovate ones and if I try to make some that would be the focus.
Some general observations that may or may not be correct: I think many or most of the ones that I have posted pics of are constructed of sheet material that is wrapped around a core that consists of the two-cavity partition as well as the anchor for the springs. All have a cam over that keeps the lid open and closed.
On this one you can see a pin in the mid-section of the charger that holds the internals in place.
This is the only pic I have of an end view and it doesn't reveal much. It does, however, reveal a very nice detail of not having to perforate the body to pin the lid.
You can see the full length seam on this one.
The demand for these seems to be quite high as they are listed for only a short time when they are for sale at prices from 50-100 British pounds. I've pretty much decided to pay what ever is needed if one of the brass chargers comes up just to have a sample in hand.
