A “Ship’s Stamp” could be modeled after an Architect/Engineer’s professional seal.
A pair of concentric circles, with a horizontal bar across the middle.
The upper half of the circle could enclose the ship’s name.
The lower half of the circle could enclose (a)the hailing port/country, or (b)the
registration number.
The bar could be reserved for (a) the master’s signature/date, or (b) the
registration no.
I wouldn’t clutter it up with too much information.
FWIW,
Gord