John,
  One might claim that the case against Sharpies is that their permanence
to fading is not known, and whether they are non-acidic is not known. I
have never researched this information for Sharpies. Pigma and ZIG markers
are considered archival and sold in catalogs that deal with archival and
curatorial materials such as Light Impressions and University Products.

Regards,
Charlie
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Charlie Sturm, Jr
Research Associate - Section of Mollusks
                     Carnegie Museum of Natural History
                     Pittsburgh, PA, USA

Assistant Professor - Family Medicine

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