The inscription on the stamp gives that a “frigate” is depict, mostly we think for a frigate a warship, but the stamp clearly shows a merchant cargo vessel without any gun-ports.
The name for a type of frigate was used also in the merchant marine, for instance the British Blackwall frigate was a well know type of ship from around 1837.
The cargo-carrying frigates were more full bodied than the naval vessels. Rigging changed through the period, square-rigged on 3-masts or square sails on the forward two masts and a lateen (later a gaff) sail on the mizzen.
Somalia Republic 1998 700 SH. SO. Sg?, scott?
Source: Aak to Zumbra a dictionary of the World’s Watercraft.