At the moment, the only way to access "Identifier-other" via CCL is to use "id-other" which is paired with 9012 in ccl.properties which is paired with "Identifier-other" in bib1.att. At a glance, it's not obvious that "id-other" is the qualifier for "Identifier-other", so I propose making an alias of "Identifier-other" which points to "id-other" or "1=9012".
Closing this due to age