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Dating scientific instruments is sometimes straightforward, and sometimes not. Rarely, a maker would date his instrument. A good example are the microscopes made by Powell & Lealand. In many cases, where serial numbers are known, lists exist of either the exact date of production or an approximation that is close can be made based on others with known dates. The address of a maker can be helpful, particularly when they moved and the years at different locations are known. Sometimes catalogs, which are usually (but not always), dated will be helpful in identifying the approximate date of an instrument. Advertisements are often very valuable as these can be used to date instruments. In some cases there is simply no easily found way and some other facts are helpful such as those presented on this page. Dating can be more of an art than a science at times, and this art is far from perfect! I have witnessed many advanced collectors miss the date of an instrument based on impression instead of facts. As time goes on, I often find myself redating some of my instruments as new information becomes available. Sometimes the facts below are helpful in at least dating to a period of time. For instance, a mystery object with a U.S. postal code must date to 1943 or later. Occasionally a patent number will help to date an instrument by its patent date. It is beyond the scope of this page to give specifics on dating, but I hope this is a good introduction. The reader should be aware of certain valuable references such as the Directory of British Scientific Instrument Makers 1550-1851, by Gloria Clifton. One should also NOT accept casual references to dating such as can be found in certain publications and the Web. An example is the catalog of the Billings Collection in Washington. Although a lot of the information is useful there are many errors in this catalog both as to maker and to date. For globes, a list of the dates of countries is often very useful. For instance, Israel was formed May 14, 1948. If a globe shows Israel as a country, that globe must date to after its date of formation.

For a table of dates useful in trying to date antique globes, please see the globe dating page.

  1. 'MADE IN'
    This is the Country of Origin or COO. It was required by the McKinley Act in the USA starting March 1, 1891. It is unclear how many makers followed it at that time, but certainly not likely before that date. This can be helpful but occasionally some makers, proud of their heritage, may have labeled their products with the COO on their own.
    The first nickel plating done in the USA started with a process in 1869, but this process did not become popular in the USA until the last quarter of the 19th century and reached its peak after 1915. Chromium plating was invented in Germany about 1925 and was not frequently used initially. Rhodium plating became commercially available in the early 1930's and was used on Wollensak Microscopes; apparently it was simpler to plate with Rhodium at that time than chromium. An American patent for that process dates to 1932. Ironically at the outbreak of WWII, rhodium use became restricted to military applications. Today Rhodium is a very valuable rare element and its use in plating is mainly restricted to Jewelry.
    First invented in NYC in 1907
  4. D.R.G.M. German registration system introduced in 1891.
  5. DEPOSE- French registration system started sometime before 1900 but I have been unable to get any more information.
    LONDON: WC, N, SE etc from 1857-8
    ENGLISH WC1, WC2 1917
    US POSTAL number code: 1943
    US Zip Code: 1962