I wrote a long time ago about a particularly attractive dial failure that happened on some cal 15 Carreras and Monacos, where the blue dial had faded/aged/changed/whatever to violet:

http://www.chronocentric.com/forums/heuer/index.cgi?md=read;id=37068

The first part of this post has a side by side of Monacos I borrowed from another post on here (I think it might have been made initially by Shaun) showing the difference between the two:

http://www.chronocentric.com/forums/heuer/index.cgi?md=read;id=61198

Well, a Carrera was recently on eBay showing the self-same thing:

https://www.ebay.co.uk/itm/Rare-Vintage-Heuer-Carrera-Automatic-Cal-15-Chronograph-Ref-1553-Blue-Dial-/232594883890?hash=item3627bc4532%3Ag%3Aj9QAAOSwZlZaL8Fq&nma=true&si=6kx0Pg1drMWhLw2aSun0j01Ni1E%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

I put in a speculative bid as much to keep track of it as anything, but it went quite low in the end. If someone here managed to buy, you did well!