The St Helena stamp is designed based on a chart of 1589 which shows Portuguese Indiamen replenishing their stores and fresh water at St Helena. The stamp was issued for the loss of the Dutch Indiaman WITTE LEEUW of the VOC at St Helena.
The chart I found in the Time-Life book by Russel Miller, “The East Indiamen”. The chart identifies all the ships at anchor. See http://www.bweaver.nom.sh/maps/linsch1.htm
The sailing ship on the left under full sail most probably arriving is unidentified.
From the left to the right from the top to the bottom of the stamp depict are the following Portuguese ships.
SANTA MARIA.
SAN ANTONIO.
NOSSA SENHORA DA CONCEPCAO.
Galleon of Mallacca.
SAO CRISTOVAO built in 1581.
SANTA CRUZ.
I do not have any information or details on these ships.
SAO CRISTOVAO is also depict on a stamp of the British Indian Ocean Territory 1999 15p sg 224, scott? It is given that she is a Spanish galleon but the only SAO CRISTOVAO I could find was built in 1581 for the Portuguese, I believe the designer of that stamp has made a mistake, anyhow at that time the Spanish flag was different as what is showed on the ship.
Chad 2013 300f in margin of stamp sg?, scott? (There it is given as a carrack, and the form is different of the hull of the ship as the other two stamps)
St Helena 1978 3p sg341, scott318.