They look like the K&T version of bushings to run the separate conductors into an enclosure.
Did I win a kewpie doll??
the two slotted smaller holes were to screw these jems into the wall, the K&T loom otruded from the two larger outside holes. The 2nd pix shows the face, where the two gooves held the K&T (unloomed) in a downward position.
This allowed the K&T exit from inside a wall to what was most likely (to my knowledge) the original wooden wiremould surface run raceway for K&T