Cassius Dio's Silver Coins

Origin
Lucius Cassius Dio (155 - 235) was a noted historian who wrote in Greek. Most notably a complete history of Rome in eighty volumes, from the legendary arrival of Aeneas in Italy, the founding of Rome, formation of the Republic and the creation of the Empire. Of the eighty volumes, over thirty six survived into the modern age (1)

Effects
As a short cut to collecting the remaining volumes Agents could rub together the two silver coins. Doing so creates silver shavings, upon brushing them away the lost pages are revealed. The negative effect of losing works by other authors isn't worth the risk as the search for the other half of the volumes continue.

Trivia
Known to emit a loud, grinding sound when trying to literally rewrite history

(1) According to the public however the Warehouse has collected 40/80 volumes