Dark Heresy 2.1
Tamr Maxif made a name for himself while serving with the imperial guard during the Chass Succession. Artillery bombardment at the battle for Uulipol unearthed a set of Astartes power armour which private Maxif was the first to notice.
The armour, which is on display in the Saint Atamere cathedral, is believed to have belonged to an Astartes slain during the great crusade. Though some have voiced concerns that the heraldry on the artifact may be inconsistent with that hypothesis.
No Astartes chapter has ever come to claim it.