I am a mail carrier. I asked and another poster posted a picture of one of these labels. First time I have ever seen one (I think). Yes, there is a barcode, note that A HECK OF A LOT OF JUNK MAIL HAS BARCODES TO MAKE THEM LOOK IMPORTANT!
I have heard zilch from the Post Office about these. They should say USPS tracking or something to indicate that they should be scanned but they don't. Frankly, I would be shocked if ANY of them EVER got a scan. There is nothing about these that would keep them out of the DPS (delivery point sort) that most carriers take to the streets in long trays and flip through quickly on the run. I due to my rough route and the fact I have no mail tray to work several trays of mail at once, case everything. So at my case I am looking at every piece and then again at the delivery point I have not ever noticed one of these for my route.
I'm sorry to say it but if I sold cards I wouldn't use this label. I would either bundle enough to sell as a package or take my chance using a first-class stamp.
