Is this a Strässle King Chair variant?  

Just to add the seller also mentioned knoll, but I have found no evidence of that either.

Here are some examples of a Strässle King chair!

Interesting that the base on the chair in question is different from the Strässle King chair photos that you posted last. Even among the 3 photos the base looks to change. I don't know anything about this particular chair but would think that the design of the base would be a key identifier, no?
Cheers.

Also, look at the design/pattern of the button tufting on the original photos versus the chair in question. They look to be very different.

Thanks vintageobsessive! I have searched and searched to find anything similar, particularly with the tufting, but to no avail. It is full leather. Even researching the more rounded shape of the backrest cushion led nowhere. I've looked to Scandinavian countries and uk. The base is also unusual in that I could find no other examples Strässle or not that matched it! It looks like a well executed, quality chair but I don't think I'm going to find its creator!

I think the base in the first picture of the examples is closest to the one I posted, as are the shape of the rosewood arms.

I think the base in the first picture of the examples is closest to the one I posted, as are the shape of the rosewood arms.

They got back to me! Strässle confirmed it is indeed one of their King chairs with custom or reupholstered cushions.