Dan - I have not marked any of my boxes with anything other than a request to call the recipient for pick up. I feel it is just too tempting for the occasional Neanderthal that might have a chance to handle it. I'm not saying that EVERY postal worker would be tempted, just that I didn't want any extra attention brought to my package.
BTW - none of my boxes arrived with excess damage and most were pristine. The postal clerks have a spiel they ask when you ship here. They ask if anything is breakable, could leak, fragile, hazardous, etc. I always say it is somewhat fragile but I don't want it marked. I have only had one that was surprised and ask why. I said that I found that the boxes arrive in better shape if they are not marked. She looked bewildered and said "That's unfortunate." I smiled sweetly and said, "It's okay, not all postal employees are as conscientious and helpful as you are." She smiled a knowing smile and processed my package, as is.