This mystery has drivin me nuts for years. I am almost tempted to take it as Zambesi it's really close. I dont sell iris ,just plant them in my perennial gardens.
I dig at Borglums iris farm http://www.borglumsiris.com/
His website hasn't been updated for years and he has a casual manner about labels.
His TBI's are labeled but I didnt care what the name was when I dug it to go with other colors that bloom in May.
I am really thankfull for your eye. I have been all over trying to find another image of Zambesi and there are not many.I dont believe its a registered iris.
That isnt important,the colors are great with emerging astilbes.