Here is mine! This one is a model 3545, which was the first of 2 versions (the one in quattro _spirit's photos is a 3546). Other than some different dial color options that changed with time on market, they only differ by movement; the 3545 has a circular F. Piget movement whereas the 3546 has a circular JLC movement, and they share a rectangular perpetual calendar module famously invented by Kurt Klaus. Below the main photo are a couple of small photos of the movement (sorry they are fuzzy - not my pics). And somewhere, I have diagrams of the PC module; if anyone is interested I'll dig them up.
And I couldn't stop here without a tale from the acquisition. I began seriously coveting the Novecento PC in the 1990s, well before I could afford a new one. I happened to be in Marburg, Germany in 2000 for a scientific conference and first saw a brand new one in a jeweler's window. I probably drove the jeweler crazy by going to see it everyday, but that moved the watch to very nearly the top of the list and I went home to save up. When I got close to the price put aside, I started seeking a new one only to find that IWC had discontinued them and no new ones were around ($%#@). So after a while, I ventured out on the second hand market and found one for about 1/4 of the original list price, but it definitely was not a safe queen. However, I must complement the spa at IWC Shaffhausen because they returned it in pristine condition.
So now she is mine and will remain in the collection until the end of time (well for me anyway).
My sincere thanks to quattro_spirit for staring this thread. I was late to the party on responding to your excellent post regarding regulator watches - I don't have one (yet) but share your interest in them.
PS: A certain watch dealer in Boston currently has one in platinum and one in yellow gold listed, and they appear to be in excellent condition.

IWC Novecento, 3545, yellow gold, circa 1990