You may want to ask the people on the Visual Resources Association
listserve.  This question seems to in their province.  The address is:

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Marianne Cavanaugh
Saint Louis Art Museum

At 03:09 PM 4/23/97 -0600, you wrote:
>The Chaco Culture NHP Museum Collection has several hundred glass lantern
>slides, hand-tinted, from the 1920s. We are currently trying to decide
>the best medium for duplicating the slides (negatives, positives, etc.)
>for research and future duplication requests. Any suggestions regarding
>the best media, photo shops, etc. would be appreciated.
>
>Wendy Bustard
>Curator
>Chaco Museum Collection
>505-277-2730
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>
>