In the best case, we'd have a complete if reduced sample where
records would appear matching oldIDs you actually represented ...
this makes it much easier to run the XSLT engines we keep in our
heads, or even engines we run in our computers, to test everything.
(List participants have been known to test each other's code in live
processors from time to time.)

The numbers are hypothetical. Let it suffice that at the end of the
day I need @oldID to match disabPrimary.

>What do you mean by "key declarations"?

By "key declaration" I mean the top-level element that sets up the
key and assigns it a name, as in

<xsl:key name="things-by-id" match="thing" use="@id"/>

<xsl:key name="types" match="option" use="@type" />
<xsl:key name="oldID" match="Record" use="disabPrimary" />

So, now that that obstacle is out of the way, howto match up to these
keys in a meaingful way?