The Plant List <http://www.theplantlist.org/tpl/record/kew-322012>
says I. klattii is a synonym of Iris spuria subsp. carthaliniae (Fomin)
There's quite a bit of discussion of I. spuria carthalinae in the
archives of the iris species discussion group. Including some about
SIGNA sources, I think.
Hope that helps, Jean. If not, maybe post your question there?