Pamela - you noted that the base of the Indiana piece in the auction referred to above looked iridised, and you asked "wasn't this to signify NEW?".
I think we've used the term "base" in 2 different ways in this thread, and that's where the confusion comes from.
1. base = the base glass itself, the glass batch
2. base = the bottom or underneath part of the item
If the base glass is clear (not coloured) then it has no significance in terms of age, etc.
If the underside (base) of the item is iridised, then that may be an indication of newer production. Not always though, as there are exceptions; for example, some old European items have iridescence on the base.