Adrian Jack was first cab off the rank this week, identifying the Kriss Kross razor blade sharpener.
Going back to the 1920s, these handy gadgets were used to give razors a slick edge for the closest shave.
Elaine Sale sent in a photo of the gadget, made by the Rhodes Manufacturing Company in the United States. They were designed for the newer safety razors, which rose in popularity after the straight razor. This specimen features a leather disc in a chrome housing.
Some other worthy guesses included a tape measure and a music box.