Mr Baslam is a fat man with old and sagging trousers and red drooping eyes like a St Bernard's and jowls like a bloodhound. His breath smells of beer. This, combined with the sign, gives an impression that is to some extent misleading: he is good at his job, and capable of getting his hands on many rare and expensive items - including banned ingredients like dragon's blood. (Gwendolen tells him that Mr Nostrum told her that Mr Baslam is the best agent he knows, and can get anything - but considering who's talking to whom, one feels obliged to take this with several pinches of salt.)
See also Charmed Life (spoilers).