We have our mail held at the post office when we're at the lake, pick it up and have service resume when we return. We do this at the "carrier annex", which is a different building than the main post office. The customer rings a bell, a USPS employee within eventually opens a locked door over a chest-high counter. The employee this time was a woman I think also works the retail counter at the P.O. some days.
They always want to see ID, but she wanted me to remove my driver's license from my wallet and hand it to her. So I did. She took it with her, presumably so she'd remember the name and address. When she returned with my mail, I noticed that she was sorta looking at my wallet which was open on the counter. I keep my permit to carry behind my driver's license because they're linked -- the permit is only valid with corroborating photo ID in MN. It's illegal even for permit holders to enter a post office armed, so I smiled and said, "I'm not carrying any weapons in your post office today." I really wasn't. I'd left the .38 in the car. She grinned right back, said "doesn't matter to me, I support the second amendment".