The PC Test Box always contains the 'Wand of Misc Tools' (a green clover item that can convert your excess Soul Runes into vitality potions... It can do something else and those who find their way into the Hall of the Gods will discover this ability).
Sometimes it also contains other useful items.
Since the RuneStone menu is active on this current update there will be an item in this chest to remove the menu from the RuneStone (Only works if Run before using the RuneStone and after talking to Haggis). This is because there are some PCs already using the RuneStone for other abilities and they are not currently running in this update.
If the chest is empty try opening and closing it more than once to refresh the contents.