Brooks Garden has many rare varieties of historic iris, some that cannot be found anywhere else. Their downside would have to be their prices, a bit to high with an average of $7.00.
Their product was average, at best. Decent sized rhizomes, although some where a bit dried when I received them. Their worst fault perhaps, is that they only ship in September, meaning that gardeners in the Eastern U.S. will have a harder time getting the iris settled in before frost hits.
Definitely shop here if you want that rare historic, but if it can be found somewhere else you may want to go there.