What is this

Did an inspection this morning and this was coming out from under window in front of house, i looked inside hole it appeared to be empty. Anyone have an idea what this is

It looks like an old septic high level alarm box.

Could it be the remains of a vintage in-wall room heater (like a modern day RV furnace)?

*BTW the GOOGLE image search algorithm says its a “birdhouse” *

This looks exactly like the discharge of a old wall furnace or space heater. This could have been in an old porch conversion or in an addition where they could not get the HVAC system to tie into. Many times since it is a box on the exterior the siding or brick cannot be matched and the box is left. Other than being drafty it posses little issue. If the system is still in the home there are other issues like: having a flue pipe under a window or a poorly maintained unit.

Thank you