Section 233. Quality marks; description

All quality marks applied to any
  article shall be equal in size and equally visible, legible,  clear  and
  distinct  and  no  quality  mark which is false, deceptive or misleading
  shall be applied to any article or to any descriptive  device  therefor.
  No  more  than one quality mark shall be applied to any article and such
  quality mark shall be applied to such article in only one place  thereon
  except as elsewhere in this article specifically permitted.
    Wherever  in  this article provision is made for marking the number of
  parts or percentage of metals, such number or percentage shall refer  to
  weight and not to volume, thickness or any other basis.