A black dial 666 found at a European watch fair...does anyone know it

Hi,
My buddy in the Netherlands has been looking for a nice all original black dial 666 for me. He came across this (please excuse the pic as he only had his phone camera at the fair) at a very large watch fair about 2 weeks ago.

Apparently the seller is a very well known local guy who is also a bit older and not very adept with the internet or overseas shipping. He also enjoys an excellent reputation.

My friend tells me it's an 8531 in "very good 1-2 condition" and much better looking than in the pictures. He also tells me the dial is excellent and the watch is 100% original. He is a trusted buddy of mine and may try to negotiate the price a bit and then send it to me.

Is anyone out there familiar with this baby?
Sorry for the poor quality phone pic, it's all I have right now.

I do notice the white date window (factory service replacement?) and absence of lume on the hands despite the t swiss t.

the date window frame looks odd, and I think the hour markers, with only 12 and 6 in arabic is also unusual ?

this great article describes many Ingenieur dials, but I don't think u will find yours in it: www.frizzellweb.com/larry/ingenieur/

there seems to be some similarity between this dial, and this one here, a post also on the authenticity of the ref 666 dial: www.iwc.com/forum/en/discussion/23273/

my opinion only - corrections welcome, especially from the many collectors who are very knowledgeable in this area.

Hi Shing,
I should mention I checked the frizzel article before posting and found essentially the same dial in white. The date frame window may be artifact? I'll try to get a better picture of it in the future.
cheers
Todd

With limited info looks in fine condition. I presume no extract from the archives in hamd ? Wold be nice if the crown is also the original one too.