Hello Don and welcome to the forum.
You can use the silver breastplate for the Larian armor quest and not for the dragon armor quest.

For the Dragon armor, this is a big thread made by Dragon :

http://lariancom.siteprotect.net/ub...&sb=5&o=&fpart=1

[Linked Image from squirrel.ovh]
duplouy.net badsquirrel.ovh
bad-squirrell.deviantart.com