It's not stamped on, but rather spray painted on. You usually ~~print~~ spray paint best before dates and batch information on the outer packaging with an inkjet spray painter. In this occasion, there was no packaging (machine failed), but there was no detection of missing packaging either, that's why it's printed directly onto the product. What these letters mean... we can only guess. Maybe the printer accidentally put out an error code instead of a date? Maybe the macine controller did a whoopsie? We'll never know.