Type AC110 5 terminal  called the Skeletal or Eiffel Tower
photo and info from Ericsson catalog - 1911  6th edition from STSF

My unit has the rarer "mother-in-law" or "bull ring" second receiver hanging on a special post under the 5 terminals of this 1905 model. This receiver could be used to cover both ears during long distance calls of low volume or as a receiver to be used by a second person listening in on a call. Micro-telephone RE 2002 resting on cradle switch, with cord RS 7021, flexible cable RS 9600 and terminal block with disc protector. The flexible cable is connected to terminals fitted under the ebonite base plate of the telephone. A Lightning protector is also present on ebonite base of AC110.

GENERATOR. 2-magnet, which rings satisfactorily through a line resistance of 12,000-15,000 ohms. The magnets of this generator also form the legs of the telephone.

RINGER. Resistance of coils 300 ohms.

Overall dimensions 12.0 x 7.9 x 5.5 inches.  Weight, 11.7 lbs.