The Office of the Comptroller of the Currency released a report yesterday saying that the Volcker Rule will cost U.S. national banks as much as $4.3 billion to implement as it forces them to sell restricted investments at a loss, Bloomberg News reported yesterday. The regulator estimates implementation costs between $413 million and $4.3 billion for banks it supervises, the OCC report said. Most of the potential costs could come from the rule’s curbs on certain investments, such as in some collateralized loan obligations. The agency also said that affected banks will mostly be those with more than $10 billion in assets and could include as many as seven community banks.