The stamp depicts the poet Virgil who wrote the book Aneis in which he describes when Julius Caesar made a call in Monaco when he returned from his triumphant victory of the Gallic Wars (58 B.C.-51 B.C.) on his voyage to Rome.
Julius Caesar is also depicted and a Roman Galley from that time frame.
At that time was Monaco a natural harbour and well known by the sailors of that time.
A “galley” in a broad sense is a long and small warship that could be of any description but generally one that could be rowed.
The stamp depicts one with one mast with a square sail and which carried a spritsail she is fitted out with a ram bow. On the after part is erected a tent for the dignitaries.
Monaco 1982 1f80 sg1600, scott?
Bosnia Herzogovina 2002 1.20 sg?, scott? (The stamp shows a Roman Galley)
Bulgaria 1975 5s sg 2436, scott?
Sources: Various web-sites