The medal's obverse bears compass rose dividing medal into four segments, each of which contains a different tall ship; waves around. Bottom left segment contains elaborate "Oceanus" and artists (JOV monogram) / © signature.
The reverse bears calendar panel surrounded by hippocamus, sea horses and sea shell. In sea shell, 1979
The ships depicted all have significance in American history. They are the Santa Maria, one of the ships that brought Columbus to the New World; the Mayflower, one of the ships which brought the first Pilgrims to America; the Constitution, the oldest active service navy ship in the world; and a Clipper ship, representative of the China trade fleet that generated so much wealth.
This is the fourth issue and in the Medallic Art Company's calendar medal series.
The circular medal measures 76.2mm in diameter and was struck in bronze, silver, and gold-plated bronze. No mintages are reported.
The edition limits of the silver and gold-plated variants are also not known to me at this point but based on the fact that the medals are marked with three digit serial numbers I would judge it to be 700 or fewer.
References: MACo 1978-075, Cal MA-1979