the face plate
There are a huge number of dial faces used in
various parts of the world at different eras in time. The three faces in these examples
help to determine what is inside the phone, regardless of the country of origin. I am
taking for granted that the phones contain original parts.
Top Photo: Large number card
holder, and no #9. This is an indication of a very early Ericofon. It
most likely will be on an old case phone. These were used worldwide, including the USA in
the beginning. I estimate that about 10% of these will have a ringer (buzzer or Ericotone)
Middle Photo: This is by far the
most commonly used face world wide, but never in the USA. These phones will never have an
Ericotone (tweeter) ringer, and about 80% have a buzzer for a ringer.
Bottom Photo: This is the face used
by North Electric. You will only find these on phones sold in the USA. About 90% will have
an Ericotone ringer (provided it's on a new case).