This cardigan was a pattern in Interweave Knits a good many years ago. The only alteration I made was to add a different collar.
It is 100% cashmere and was made using an industrial yarn that was so fine I had to use 6 strands to achieve the thickness (a DK I think).
I love this cardigan and wear it so much. It has proved extraordinarily hard-wearing. I think this may be due to a combiation of knitting with multiple strands and the firm tension .
If it wears out, I will definately have to knit a replacement!