Gameserver/Data/Stats/Armor/9400-9499.xml
Open that file, and ctrl+F 9417.
You can now see how the stats are which is like this:
<item id="9417" name="Dynasty Breast Plate - Shield Master">
<cond msgId="1518">
<player class_id_restriction="90, 91, 99, 106"/>
</cond>
<for>
<add order="0x10" stat="pDef" val="226"/>
<enchant order="0x0C" stat="pDef" val="0"/>
</for>
</item>
This is the restriction:
<cond msgId="1518">
<player class_id_restriction="90, 91, 99, 106"/>
</cond>
Copy that and add it on the other armor parts you want to in gameserver/data/stats/armor
to add other player classes to the restriction, open table: char_templates in your DB to see other class ID's