The Dimming Era
This is a +1 breastplate. This armor is designed to be used while swimming so it is only considered to have an armor check penalty of -2 for swim checks
The marines of Cihh have found that, instead of making breastplates from metal, they use the molted shells of great sea turtles. While the shells are rare, the large population of turtles living around Cihh provides more than enough. While started by the marines, it is not uncommon for other sailors to fashion armor in the same way, and while it can be slightly suspicious to those of questionable motives, the marines themselves hold no claim over all of this armor.