I didn’t get a complete answer - I was advised that “RMRMRMRM” was etched to allow the identification of the franchiser that sold the chip, however, the vendor was unsure of the supplier of the memory chip. Of the sample of USB’s we’re testing prior to purchase, some are marked CHINA, and others are MAYAYSIA – both types having the “RMRMRMRM” etching on top of “Sandisk”.
Similar to your comment, the only references I can find on the web seem to also indicate a belief that “RMRMRMRM” means it’s likely bad or rejected. I guess I was hoping for some confirmation from Sandisk that they do this with their rejected chips. Do you happen to know if Sandisk monitors the forums?