i am looking for iris from the late 1600's and 1700's - do you have any ideas where is should start this quest
The ones that come to mind when you think of bearded iris are Iris swertii, Iris florentina, Iris germanica, and Iris pallida. Of course other species types of iris would work too.
This company has an excellent reputation on the Garden Watchdog, you might want to look there.
"Offering unique, endangered heirloom bulbs from the 1950s back to the 1200s, many of which are available nowhere else."
Just passing along info, not affiliated with any company.
Here is a link that might be useful: Old House Gardens - Heirloom Bulbs
Many people have lots of I. florentina and I. pallida available for trade. You probably could get the other two also by trading.
Two other bearded iris from way back are Sambucina and Iris variegata.