I am an "officer" and general managerat a Virginia based financial institution. We do not have any policy against firearms carried by members (openly or concealed).We are not permitted to ask about or see the items thatfolks choose to leave in their safe deposit box. That's why there is a private room to deposit and retrieve items from after you get your box. Even financial institutions that do forbid firearms could only cancel your box if they somewhow found out - which they never should. It is standard policy for all financial institutions to make sure their employees have no clue what is in any of the safe deposit boxes. The contract you sign may prohibit certain items, but no one but you will ever know what is in there. To open a safe deposit box without theowner present generally requires a court order, and thena very expensive call to a specialized locksmith to drill the box, etc.
No item would be forfeited just because you don't follow the rules. Safe deposit boxes are highly regulated. The worst possible cicumstance is YOU tell the institution you have a prohibited item in the box. Even still, if you don't voluntarily remove it, they'd have to go to court to get a court order then hire the locksmith (which you would payfor under this circumstance). Your contract may be cancelled. But that's it. No arrest or forfeiture or anything like that.
Over the years, I've heard stories of people putting AWFUL things in safe deposit boxes, including a dead, rotting fish. This was way before my time. I was told it took over a week just to get an order to remove it, and it shut down the branch meanwhile.