Dark stained low slung armchair, anyone seen it before?  

It does not look like Mogensen to me at all, fwiw.
What wood is it under the black? Is the black original? Does the construction look American, European, etc?

Me either Leif, I think the seller is just putting a name to it. It's still many miles away. It looks a bit heavy and awkward to me. It looks black in the pictures but is actually a very very dark brown. The way the back cushion is built into the frame is also strange looking. I think it's European alright, but that's just a hunch. Does it look more modern to you?

Try Camerich " SIMON " chair.
Lexi.

Thanks Lexi! I'm glad I didn't go for it, I found a lovely Eames vitra armless chair I plumped for instead!