Good question. It is not a capital 'b' but a German special character called " S Z Ligatur", a combination of the letters S and Z to denote a sharp-spoken S. If you write a tall S and attach a small, round z to it you almost have it.

It has made its way into HTML as ß but is currently on its way to extinction in modern German. The generally accepted way to replace it is via two S, so I won't be terribly upset if you write "Classen". In fact most of my email and login accounts are written that way since surprisingly enough there is no ß in 7-bit ASCII...

As a good safari tour guide I am very concerned with the protection of endangered species, so I will have some ß's hanging out on my pages. Please don't feed them. Thanks!