Definição

• Blister.  A casting surface imperfection caused by dirt in the mold. It is removed on the cast piece by chasing. Breen reports blisters on the U.S. cents struck on copper-coated zinc composition introduced in 1959; it was cured somewhat by annealing.
  References:                                                                                                                                
  NC9 {1988} Breen, p 234.

  excerpted with permission from

  An Encyclopedia of Coin and Medal Technology

  For Artists, Makers, Collectors and Curators

  COMPILED AND WRITTEN BY D. WAYNE JOHNSON

  Roger W. Burdette, Editor

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