This is Mix & Genest intercom type B3010, can be found from 1910 and 1914 catalogs. Handset is changed to Ericsson one.
This one is for 10 lines, it has push button selection and also DC ringing with same button. Extra bell must be added to the phone.
There is a small paper tag inside:
Kat. Nr. B3010
Nr. 11447
rev. 27/12