Archivist's will

You touch an tiny lifeless object that you wish to preserve and prevent from alteration, and it becomes protected by magic for the duration. You and the creatures you designate when you cast this spell can interact with the object normally. You can also set a password that, when spoken within 5 feet of the object, suppresses this spell for 1 minute. Otherwise, it is impassable until it is broken or the spell is dispelled or suppressed. 

The spell level required for the item to be preserved will be proportional to its size. A small object will require casting this spell at level 4, medium object at level 5 and large object at level 6. The gold dust required as consumable material component and time needed will be 10 times more when up casting the spell per level. The duration is also possible to lengthen by multiplying the number of years of preservation, i.e. preserving a large object for 3 years would require 75,000 gp worth of gold dust which the spell consumes, and the spell casting would take 30,000 minutes. Multiple spell casters can help to divide the time needed for spell casting to expedite the process, the casting time can be divided evenly per number of spell casters with any reminder round up.