Storing coins

I am advising a client on coin storage facilities and would
appreciate if anyone can provide further information on the
following. The collection comprises mostly of modern i.e. 1990's
commemorative coins--more than 3 thousand. Up to now the coins have
been stored in their original casing: each coin is placed inside a
clear two piece round plastic holder and this in turn placed in a
case which internally, on one side is lined with a velvety material
and, on the other, is lined with a padding material wrapped in
fabric. Externally the case is covered with a plastic covering. This
case also contains the original certificate accompanying the coin. A
large majority of the coins have suffered decay--staining, tarnish
etc, but we cannot be sure whether this can be attributed to the
casing materials or to the storage conditions which were not
controlled up to now.

Does anyone have any information on the stability of the materials
comprising the plastic holder and the case used in commemorative
issues (I assume this is a standard way of presenting these coins)?
Is it wise to store the coins in them for long term, or is it better
to transfer the coins into other cases such as paper envelopes of
Mylar flips? It is of course important that the coin and certificate
remain together during storage. The coins will be stored in a room
where the temperature and humidity will be controlled and monitored,
but there will be no active gaseous pollution control. Any
suggestions are much appreciated.

Eleni Loizides


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                  Conservation DistList Instance 19:5
                  Distributed: Saturday, July 9, 2005
                        Message Id: cdl-19-5-026
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