OY Puhelin ja Sähköpaja's wall phone
This is Finnish made telephone, from OY Puhelin ja sähköpaja or PSP (Telephone and electric factory) in Helsinki.

Handset looks like Finnish Puhelinteollisuus handset and rest of the parts like Erisson. Ball are on the bottom of the telephone

Case made from birch plywood, stained to brown and shellac on top.