It is unclear what the type designation of this phone is. Heemaf made them for PTI. PTI came into existence after WW2 when Siemens Holland could no longer supply equipment to the PTT.
PTT requested Philips instead to supply certain telecommunications equipment for the rebuilding of their network. The exchanges and installations developed by PTI were later exported all over the world.
Heemaf supplied telephones for these business networks, of which this is an example. It is a version of the phones Heemaf supplied to the PTT.