Question about the reference 3531

Hi gents!

I have a question. A friend of mine is looking to get a ref 3531 in rosegold. The thing is that he noticed that some of them have a gold rotor and some of them have a steel rotor.

As far as I know, IWC switched movements during the production run from a JLC 891 movement (which has the gold rotor) to a 891/2 movement. The meterial being used for the rotor changed with these different movements being used.

Can someone give me some more information about this and about the watch in general? Much appreciated gents :)

Have a nice day all.

Indeed, some golden 3531 have 18 - or 21 carat gold rotor weights.

All 3521 and 3532 have 21 carat platimum rotor weights.

But no idea whitch tranche(s) of the golden 3531 were equipped with those 18 carat weights.