I would say, step 1 is to take lot's of good pics...close-ups, and clump shots 2..record everything you know about the iris..in this case, it's tall, and big..so probably a TB. ,does it have PBF?, does it have an aroma? what does it smell like? grapes? rootbeer ? perfume?..3 post the pic that best shows the bloom on the forums...you might get lucky, and someone will say" I think it's .....whatever...4 spend some time searching the vendors websites...most have their search set up to search by color.....Then, assuming you find one or two "possibles", check the AIS wiki for more info on the possibles, look for things that will confirm, or deny ID. then, let's say you find one iris that you are FAIRLY sure is a match...Ask your "iris buddies' on the forums "Anybody grow.......?, if one does, he may offer to either send you a piece, or have YOU send one to HIM, for comarason growing. If no one has it, try to buy one from a vendor, and grow for compasison. If it's a match...you did it !!
If it's NOT a match.....repeat steps 3 and 4
...good luck !....Arlyn