Not easy to find absolute proof, however.
For "(wax) rims" see the first reference below and, for another example:
http://www.austindentalassociates.com/denture.htm


For "trays":
look into
http://www.straumann.com/de/com_index/pc_index/pc_solutions/...
and
http://www.straumann.com/com_index/pc_index/pc_solutions/pc_...
for the equivalence of tray with German "Löffel" in this context.
Another example of tray in the second refernce below.

combinations of wax rims and trays you also find in
http://www.auth.gr/dent/en/depts/kiniti/kinitipre/kinitipre2...
(there the trays are specified as "impression trays")
and:
http://www.auth.gr/dent/en/depts/kiniti/kinitipre/kinitipre5...
(greek origin, but looks good quality English)

Greetings,

Nikolaus

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Note added at 2003-03-23 17:57:38 (GMT)
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http://www.geocities.com/klemetti/lectures/CRregistration.ht...
gives the logical options of
\"wax records\" or \"occlusion records\" as alternatives to \"rims\"