We know from Tomb Raider 4 and 5 why the iris is important: Werner's greed for it whether or not Lara beats him to it, despite the warning that it was booby trapped in TR4, and Lara stealing it from him and his father (I think. Werner himself couldn't own VCI being an archaeologist and all.) in TR5.

But it first appears in Tomb Raider 3 in Lara's treasure room, just beside the Dagger of Xian. I don't know if it was Andy Sandham or somebody else who redesigned Lara's Home for that game, but what was their thinking when they added it?

Did they know in advance it would be used in later games and wanted to show us it in a secret as a form of foreshadowing?

Or was it added just because (perhaps to show off Core's animation skills?) and they picked it as a catalyst for Lara and Werner's damaged friendship because they thought of giving something so strange looking and mysterious enough to be a major plot macguffin at least some form of origin story?

Pity they couldn't do that for Mike's Mystical Head amIright? ;)

http://tombraiders.net/stella/walks/TR3walk/screenshots/traingoldhead.jpg

I'm still trying to figure out how the hell The Arc of the Covenant got into her house.

Maybe she bought it from Rick Dangerous? ;) Thumb up if you know that game. It was Core's very first.