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  2. Sheldon coin grading scale - Wikipedia

    en.wikipedia.org/wiki/Sheldon_coin_grading_scale

    Example of an Early American Cent - the coins that inspired Sheldon to create a more precise grading scale. (Courtesy of the National Numismatic Collection, National Museum of American History [photograph by Jaclyn Nash].) The Sheldon Coin Grading Scale is a 70-point coin grading scale used in the numismatic assessment of

  3. Logarithmic timeline - Wikipedia

    en.wikipedia.org/wiki/Logarithmic_timeline

    A logarithmic timeline is a timeline laid out according to a logarithmic scale. This necessarily implies a zero point and an infinity point, neither of which can be displayed. The most natural zero point is the Big Bang, looking forward, but the most common is the ever-changing present, looking backward. (Also possible is a zero point in the ...

  4. Coin grading - Wikipedia

    en.wikipedia.org/wiki/Coin_grading

    Coin grading [1] is the process of determining the grade or condition of a coin, one of the key factors in determining its collectible value. A coin's grade is generally determined by six criteria: strike, preservation, luster, color, attractiveness, and occasionally the country/state in which it was minted. Several grading systems have been ...

  5. Numismatic Guaranty Company - Wikipedia

    en.wikipedia.org/wiki/Numismatic_Guaranty_Company

    The NGC grading scale is based on the 70-point Sheldon coin grading scale. Strike designations include Prooflike and Deep Prooflike for circulation issue coins and Cameo and Ultra Cameo for Proof coins. Coins deemed high-end for their particular numeric grade receive a "Plus" designation. Coins considered attractive get a "Star" moniker.

  6. Chronology of the universe - Wikipedia

    en.wikipedia.org/wiki/Chronology_of_the_universe

    It is not known exactly when the inflationary epoch ended, but it is thought to have been between 10 −33 and 10 −32 seconds after the Big Bang. The rapid expansion of space meant that elementary particles remaining from the grand unification epoch were now distributed very thinly across the universe. However, the huge potential energy of ...

  7. Photon epoch - Wikipedia

    en.wikipedia.org/wiki/Photon_epoch

    In physical cosmology, the photon epoch was the period in the evolution of the early universe in which photons dominated the energy of the universe. The photon epoch started after most leptons and anti-leptons were annihilated at the end of the lepton epoch, about 10 seconds after the Big Bang. [1]

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  9. Third-party grading - Wikipedia

    en.wikipedia.org/wiki/Third-party_grading

    Third-party grading (TPG) refers to coin grading & banknote grading authentication, attribution, and encapsulation by independent certification services.. These services will, for a tiered fee depending on the value of the coin, "slab" a coin and assign a grade of 1–70 on the Sheldon grading system, with 1 being the lowest grade, with only faint details visible to 70, a practically perfect ...