Jerkin

A Jerkin (Jerkin Robe in the Japanese version) is a common Robe-class bodywear available throughout the Golden Sun series.

Basic Description by Game
A Jerkin increases the wearer's base Defense by 26 points. As a common item, it can be bought repeatedly from vendors for 2400 coins each, and sold for 1800 coins each.

In Golden Sun, Jerkins are sold in Kalay and Tolbi, and can be equipped by Ivan and Mia. In Golden Sun: The Lost Age, they are sold in Yallam, and can be equipped by Jenna and Sheba. In Golden Sun: Dark Dawn, they are sold in Te Rya Village and Belinsk, and can be equipped by Karis, Rief, Amiti, and Himi.

Analysis
In Golden Sun when Jerkins can first be bought in Kalay, they can be good buys even if your mage-style Adepts Ivan and Mia are equipped with the likes of Adept's Clothes, as well as the Fur Coat and the China Dress. Don't be too hasty in buying them, though, because the strong Clothing Artifact Water Jacket can be easily fetched in the nearby Hammet Palace in Kalay.

In Golden Sun: The Lost Age, Jerkins are not really worth your money to buy: As soon as you get the Lemurian Ship and are able to start sailing the Great Eastern Sea, Jerkins can be bought in the armor vendor at Yallam, and they do have more defense than the things Jenna and Sheba could be currently wearing, such as Adept's Clothes and the Full Metal Vest. However, an even stronger piece of common bodywear that can be equipped on the two girls is available for buying in the Great Eastern Sea: The Silver Vests that are sold at Izumo. Also be aware that a far superior Robe Artifact, the Blessed Robe, can be bought at the same time at the general vendor at Champa, so you would ideally buy that first and then consider a Silver Vest or two, without any consideration paid to any Jerkin.

In Golden Sun: Dark Dawn, Jerkins do provide a good Defensive increase over the bodywear Karis, Rief, and Amiti would be wearing. Once reaching Morgal, however, Jerkins can be quickly replaced by the Silver Vest found in Port Rago, as well as the various Artifacts found in the region.