Ian, I don't have a mic to measure the bore diameter. I was told the chokes from the seller. The choke mark asterisks are not on the side of the chambers. According to the seller, this gun was refinished by Browning UK about 1984, and has sat in a safe ever since. It was displayed at the 1984(?)CLA Game Fair in the UK as the oldest know Superposed in the UK. It shoots just fine and ejects both shells on the ground within inches of one another, clean over my shoulder. Thank you Mr. JMB.

Scotty