I think you will find that the two main uses for guns of such small nature was either as swivel guns, whether on a boat, ship or fort's rampart or as largely decorative arms in stately manors, castles and similar buildings owned by the aristocracy & wealthy.
I agree that those marks are probably those of the foundry. You might consider it worthwhile to engage the experts to tell you what they can at
https://www.basiliscoe.com/