Vass / Museum Calf, Slipper, Coin Loafer. The marble-like pattern of the Museum Calf, often called the marble of leather, is very beautiful, and the quality of the leather is excellent. Vass Model: Slipper Upper: Museum Calf LAST: U Color: Dark Brown Size: 39 (24.0cm) Outsole: Leather / Half Rubber Style: Coin Loafer Accessories: Shoe Trees