I think the easiest way to tell if a coat is silk, other than appearance, is that it feels cool to the touch.
The term 'silk' means so many different things to different people and is referred to differently. I've heard of modified silk, hard silk, soft silk, warm silk and cool silk.
I like the term 'cool silk'. It's the most accurate to me in describing an ideal coat texture. I don't think it has the cool feel unless all the attributes of a silk coat are there.
But then, I could be totally wrong.....
, but just going by my experience so far.