The brand is Totes by Isotoner. It has an automatic release and wind vents. Diameter when open is 51".
This is a huge umbrella. I don't even know why I bought it. It was probably when I was working at the Trinity office and I was inspired by Dr. Leithart's umbrella (except, of course, he actually *used* his. Mine just sat around being awkwardly too big for one person).