This section is from the book "School Needlework. A Course of Study in Sewing designed for use in Schools", by Olive C. Hapgood. Also available from Amazon: School Needlework: A Course Of Study In Sewing Designed For Use In Schools.
Thimbles have been in use only about two hundred years. They are made of metal, celluloid, or aluminum, with either an open or closed top. The indentations on the surface are made to hold the head of the needle firmly.
In manufacturing metal thimbles, a thin disk or blank, about the size of a silver half-dollar, is first cut from sheet metal,and is then drawn into a cap. This cap is heated and tapered, and the edges rolled; the top and then the sides are indented, and it is completed by being polished and plated.