You can turn in the green+ quality gear from boxes/bosses for seals. You have to be at least Private Second Class though.
1.21 patch notes has a list of all the U/U gear you can turn in for seals
http://forum.square-enix.com/ffxiv/t...l=1#post580985
Some of the world NM stuff can be turned in too, but the drop rate on some of the stuff is awful.
My gf and I can duo the dungeon as 38GLA/38CON so you don't have to be 50 to do it, it's probably way faster, though.
