My mother had a small bit of very thin brass about the size of a credit card, with a slot running from the edge to the middle of it. She told me that it was for polishing brass buttons on uniforms by sliding it around the shank of the button, leaving the button on top and the uniform below, so that the polishing cloth and polish would not get onto the uniform - slide it under the button and rub away because you wouldn't get polish on the uniform.

Does anyone know what it would be called, or where to get one these days? Seems useful still!

Any ideas? I'm sure that someone in the Great Rabble will be able to help out on this.