ATEA phone from the 20s. In this period ATEA was part of Automatic Electric (Strowger). It is therefor no coincidence that this telephone is based on the Automatic Electric Monophone.
Although this is an autonomous telephone, it does not contain a signaling device. A seperate ringerbox is needed for this telephone.
The handset is a typical ATEA design. Already patented in the 20s, you can find this model, with minor adaptations, on ATEA telephones well into the 1960s.
This is a very rare telephone, nowadays.