EDIT

    //NOTE still need to discuss, if the identity cache for derived units

    //should also include the identity cache for field units (see also #5951).

    //This may make sense for searching, but is less comfortable in

    //tree representations.

    //For search it might be not so urgent if showing both the identity cache

    //followed by the titleCache whcih includes field unit information.

    @Override

    protected String doGetIdentityCache(DerivedUnit derivedUnit) {

        String specimenLabel = getSpecimenLabel(derivedUnit);

        if (isBlank(specimenLabel)){

            return getTitleCache(derivedUnit);

        }else{

            //NOTE: in future we may add further information if not both data are given

            //      collection code/label AND unit number

            return specimenLabel;

        }

    }