I believe it is a map roller for multiple maps. Each map would have been attached in one of the visible slots. The map would be selected by pulling down on the rope close to the wall, then reversed to display the chosen map. My memory of it is vague, but I once saw something like this in an old bank office that was being dismantled in about 1960. I do not recall seeing it operated. There is likely some sort of spring loaded ratchet mechanism involved, hence the noisy operation.