UPDATE !! The matter is resolved.
Earlier today I sent a detailed e-mail to the contact which MWSY supplied.
A short while ago I got off the phone with him, a senior member of corporate management who asked me not to identify his position. I verified his position, however.
He succinctly made the following points clear: 1) he apologized for my experience, 2) he said the guard exceeded his authority, as they are merely to request that people remove sunglasses, hats, etc., 3) he didn't fault the manager for backing the guard up, although I mentioned it in my e-mail, but didn't push it on the phone, 4) he stated that PNC has no policy regarding the carry of firearms by customers, 5) he will ensure that instructions are given to the security guard company (Allied, I believe) that gun carriers are not to be approached for that reason, and 6) that employees or contractors who object or state their fear of open carry are to be told (essentially) "Our policy is we do not involve ourselves in a customer's decision to carry or not carry a firearm".
I was ready to offer to discuss open carry or firearms matters with the branch employees, because of what I perceived to be an atmosphere of nervousness created by the branch manager's fear and dislike of openly carried firearms, but the executive made it clear that he felt no need to do any hand-holding on #6.
Bottom line, there is no written policy, and the executive made it clear that if the bank were to involve itself in such matters by posting it would be dictating (or making illegal) a choice better left to the bank customer.
Thanks again to MWSY, and to PNC.
Carry on! (pistols only, please)