Antique Brown Marble looking Door Knob, Some type of Stone, Stamped Italy

Here we go again, Really Door knobs Collectible? Well this one along with a couple others caught my eye. The estate was not remodeling but found these in a box in the basement, Here in Pennsylvania. Must have belong to the Previous owners. Well back to the research board. trying to figure out when they were Mfg.? and what type of Stone.