This type of analysis should always be performed by a professional skilled in the art of preservation and restoration. However, there are certain visual tests of general appearance which can be performed by the layman to make an initial determination concerning an item s authenticity. There are few exceptions to obvious wear on early scientific artifacts, even if such instruments have been properly used and well maintained in a laboratory environment. Even later instruments, in appropriately conserved collections, have obvious evidences of wear peculiar to their function. Such wear is measurable, but can usually be detected by a visual and tactile examination alone.
Normal wear is peculiar to functional surfaces.
An example is the leveling, or tangent, screw. In general such components are used near the center of their range of motion, and the resulting wear-pattern falls predominantly in the center of their travel. Such wear is relatively consistent whether or not the instrument has been well-maintained while in service. This wear is also accelerated when an instrument has been used in a hostile environment such as a desert with blowing abrasive particulate, or in a mining, tropical or coastal operation where corrosion can impact functioning surfaces. This occurs particularly on thumb screws, focussing knobs, leveling screw knobs, and lock screw knobs.