After a kind "gift" of Darth Panda, the peruvian clones of the Mackerel class.
First, 2 de Mayo, head of the class of 4, depicted as it appeared in 1957. The second boat is Iquique (last 2 ships without deck gun), with the new numeration and name, in 1959. The third one is the second boat of the class, Abtao, depicted as it was in the mid 70s, with new enclosed fin, conspicuos bow sonar dome, Mk.37 capable, but retaining the gun. SS-42 is now a museum ship.
Credits: Darth Panda, of course! His Mackerel class was, as in real life, the starting desing of the drawings shown here.