"Two Slots Built into a wall around knee high in a 1955 house with what appears to be wooden “reeds”"
A: "Old style audiophile setup. The bottom slot is for a pull out record player that used the “reeds” to hold the frame in place while the player was pulled out. The top spot is for the amplifier. There may still be wires and/or speakers in the walls/around the house."
this is all lifted from a reddit thread.
https://www.reddit.com/r/whatisthisthing/
https://www.reddit.com/r/Whatisthis/
Most humor sites repost reddit stuff.