Early 20c white marble substrate for b/w photos

I will appreciate any references to information on the history,
technology or conservation of b/w enlargement media using white marble
or glass as the emulsion's substrate.  Please email or post to CDL.

John Scott
New York Conservation Center, NYC

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                  Conservation DistList Instance 7:23
                 Distributed: Saturday, August 28, 1993
                        Message Id: cdl-7-23-003
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