Why do some stamps have barcodes and numbers like this? : r/USPS

Postage stamp - Wikipedia

AMS :: Feature Column from the AMS

Really TEMU???!!! : r/USPS

USPS stamp printed at PO what is this barcode on stamp? Is it traceable 😬 : r/USPS

Really TEMU???!!! : r/USPS

Mariachi Stamp

What do those barcodes on my mail mean? - Extend Your Reach

Why did I receive a letter without a postage mark? Doesn't the USPS have to stamp all the mail? - Quora

USPS Set of 8 Notecards Folio VINTAGE 1990s SANTA Christmas Stamps

National Marine Sanctuaries Stamps