1.75" from set picturing the Whiz Kids. Typical buttons have open backs with removable spring pins. This is our first seen with a tin-covered back which has a fixed horizontal bar pin. Cello in reflected light has some tiny rub marks in the facial area, a couple of very tiny air dots and lower portion of button is just flattened a hair. Under normal viewing, piece still displays totally clean. Rare in this form and first we've seen.