Some old South American Indian cultures calculated on quipus, which were necklace-like objects where they would tie on the dangling strings different kinds of knots to indicate a number. The type and placement of the knots indicated the number. Subtraction involved untying knots. It was commonly used for accounting, trade and other business. The conquering … Continue reading Quipu

Offered here for download or online viewing is a new pdf ebook by David Cycleback.  It is a beginner's guide to identifying common materials in antiques, including glass, gems, wood, metals, plastics and more.  The 100+ pages ebook is heavily illustrated in color and is designed for the beginner. download guide . , , , … Continue reading Introduction to Identifying Common Materials in Antiques (ebook)