Well, all the shipping and mail is xrayed so if it's cash, workers know. Or is that just a rumor?

Funny not-funny story: I always use uspo because recipients complain about others so much. So last month, I shipped 2500. of original art to my bestest dear repeat clients, insured, sig required, in Michigan. We all grow concerned and start tracking that box. Lo, and behold, the Phoenix postal terminal, sent the box to freaking Anchorage Alaska, who then sent it to Michigan. Damn well know that was the work of some careless human mail sorter.