Marble (toy) conventions. Additionally, many glass artisans produce art marbles for the collectors' market only, with some selling for thousands of dollars. Marbles are made using many techniques. They can be categorized into two general types: hand-made and machine-made. Marbles were originally made by hand. Stone or ivory marbles can be fashioned by grinding. Clay, pottery, ceramic, or porcelain marbles can be made by rolling the material into a ball, and then letting dry, or firing, and then can be left natural, painted, or glazed. Clay marbles, also known as "crock marbles" or "commies" ("common"), are made of slightly porous clay, traditionally
Toy piano in that they possess keys. Toy pianos are usually no more than 50 cm in width, and made out of wood or plastic. The first toy pianos were made in the mid-19th century and were typically uprights, although many toy pianos made today are models of grands. Rather than hammers hitting strings as on a standard piano, the toy piano sounds by way of hammers hitting metal bars or rods which are fixed at one end. The hammers are connected to the keys by a mechanism similar to that which drives keyboard glockenspiels. Toy pianos ostensibly use the same musical