I received Eidolon's Cloth Mantle of Force from the Overseeer Season 3 quest Tarinax's Head. It came from the Bonus chest and is flagged "No Trade". From memory I believe my Bonus Chance had been 70%. I can't recall which agents were used, although I don't imagine that's relevant. I got this on my Berserker so it's functionally useless since it's also flagged "Mage Only" even if he wanted to use it. I have never seen any Overseer reward before that wasn't flagged "Heirloom" and given the account-wide nature of the Overseer system and the randomly-generated nature of the rewards it seems extremely unlikely that the intent would be to give rewards that were both class-specific and not tradeable within the account.
I just got the same Eidolon's Chain Mantle of Force today. I see this has been confirmed, but hasn't been fixed in over a month? Come on folks, we just had a patch put out this morning. We'd really appreciate it if it were fixed so we could make use of the items.