Having contact with the original owner of a slide rule that remembers the year it was purchased helps on determining the age. In general it is safe to assume a linear production rate between the rollover dates particularly for the common types rules.Other Slide Rule dates are currently in development. Please refer to the museum library and individual galleries as this page is being built. Serial numbers can be used to approximate the manufacture date of a given rule however not necessarily the sales date.
While there are plenty of commercial cleaners available, it's just as effective to clean gold with what you already have.A diamond certificate is a report that attests to the authenticity of a diamond.It is a reliable and accurate statement of the diamond's identity and grade based on an internationally recognized system.The electronics, computers and communications industries, power engineering and much of the chemical industry of today were founded on discoveries made possible by the battery.Pioneers It is often overlooked that throughout the nineteenth century, most of the electrical experimenters, inventors and engineers who made these advances possible had to make their own batteries before they could start their investigations. the World was starting to emerge from the Stone Age. C., Mesopotamians (from modern day Iraq), who had already been active for hundreds of years in primitive metallurgy extracting metals such as copper from their ores, led the way into the Bronze Age when artisans in the cities of Ur and Babylon discovered the properties of bronze and began to use it in place of copper in the production of tools, weapons and armour.Most diamonds appear colorless but actually have slight tones of yellow or brown.