From a quick google, Brown and Pank Ltd appear to be a now deceased London wine merchant that ended up being owned by Watney Mann, a London brewery.
I stumbled across some pictures of old rum bottles bearing the Brown and Pank name and, as it was common for merchants to bottle both rum and port, this is more than likely a very old BOB. If anyone really wanted to find out which shipper produced the wine they could probably find the archives of Brown and Pank by starting with an enquiry to Watney Mann.
"The first duty of Port is to be red"
Ernest H. Cockburn