This iris flowered for the first time here in 2018 and does seem to match the descriptions. As there is little provenance, I can only guess that it might be right.
Grace Sturtevant x ? (?... sister to GS?) TB-Mla-S6D (AIS Checklist 1939)
With its clouded yellow standards and the rich depth of Grace Sturtevant in the fall should prove a rival for Bruno as it is even a richer bronze of the Dominion race. (RS Sturtevant; AIS Bull. No 43)