A forbidden lore (Daemonology) check to reveal the information would have a +30 bonus, since that's extremely basic information for that field.  A common lore (War) check at a -30 penalty would also reveal the stages and nature of daemonic incursions.<br/><br/>Concerning the platoon standard, it's still in the hands of the false guardsmen, and they likely wouldn't allow it to be burned without a fight unless their commanding officer was dead or telling them to surrender the colors.  Battle standards are known to inspire particularly ferocious fighting in Imperial Guardsmen, even though some regiments disdain them because they tell the enemy exactly what kind of units are attacking.