Maybe a Spellcraft Check to sort one Aura from Another via Detect Magic.
I've alwyas allowed Lead-Lined Flasks to conceal the Aura Within (note Lead-Lining on Exterior, as opposed to Interior; Lead Posioning and all you know).
I figure if Lead can block most Divinations and so forth, it should block things like Detect Magic as well.
Lead does block detect magic and could be concealed by a covering layer of unfired clay or the like. In the past I've written up lead crystal as a special material for potion flasks - it's also nice and sparkly so it's used for ordinary expensive glassware as well.