[Dave Moll]

The internals of the two 'phones (and the wiring diagrams as far as can be seen from this distance) do indeed look identical. As they are powered by local batteries (a standard "D" cell will be a suitable substitute for the orginal - which is probably best kept as a display item as a lovely example of a period cell), they should be possible to connect together to communicate with each other.

As Dag says, a close-up image of the wiring diagram pasted to the case should provide the information needed to connect them up.

Depending on the type of transmitter (microphone) in the modern handset, this should be fine for getting the 'phones working. The original handset would have been of the carbon-granule type which varies its resistance according to the pressure waves of speech. As long as the modern one works on the same principle (rather than a magnetised coil that generates a small varying voltage) you should be OK, though the modern electronic (electret) substitutes for carbon-granule transmitters will require a minimum of 4½V (e.g. three "C" cells) rather than the 1½V supplied by the single cell.

Regarding the bell ringing when you operate the magneto, this may mean that you have the magneto output feeding back to the internal bell rather than to the line to ring the remote bell. Again, the wiring diagram should help to sort this out.

By the way, what's hiding behind what looks like a brown paper bag?