Probably means it's cylinder bore, especially if it was an issued gun. But not all fixed bores are cylinder bore. Before changeable chokes became mainstream many guns had fixed chokes in full or improved for hunting and skeet/trap. Some side by sides and over unders even had one of each. The logic being the full choke was second for a follow up shot which would theoretically be longer distance.
Probably means it's cylinder bore, especially if it was an issued gun. But not all fixed bores are cylinder bore. Before changeable chokes became mainstream many guns had fixed chokes in full or improved for hunting and skeet/trap. Some side by sides and over unders even had one of each. The logic being the full choke was second for a follow up shot which would theoretically be longer distance.