Trying to figure out why a PO Box would do anything to prevent the postal carrier from stealing items.
Because the items would be sorted into the postal box without the carrier ever knowing. He would never see 'em.......
I use a PO Box for all my incoming purchases...except for certain mint products that come UPS. When I mail stuff sold on eBay it gets scanned by the lady taking it where we drop it. I have developed a good friendship with her and she scans everything for me so I know it's in the system. After that I have no control over it and neither do you. I have had packages come to my PO, then go to VA and come back to my PO for no unknown reason other than someone can't read the zip code or scan. As for the OP having coins stolen on the way, it is NOT necessarily your postal carrier. It could be anyone from the outgoing PO and anywhere in between the sender and your distribution center to the carrier. Your best course of action would be to ask whoever you buy from to please make sure you have a tracking number because of theft in the past. If they print their label from eBay you automatically get a tracking number.
I had one with insurance and tracking and my claim was denied. Since it was a regular envelop, even though heavily taped and reinforced inside, USPS claimed that regular envelopes are never considered secure. Even though they took my money for insurance when I mailed it, they would not consider a refund of those charges because I should have known better.