This ship has a dragon head at one end, and a curled tail at the other. The three shields do not appear to overlap at all, they are simply beside each other.
This scan shows two markings stamped into the underside of the ship - I don't know if they are from two different ships, or both markings are on one ship. One marking has the words "TINN PER" and "NORWAY". The other marking has the words "STØPT TINN" and "PEWTER".