Yes, this is a very delayed reply, but there may be others with the same question.
I think you're right that the trailing characters are packaging.
I've used SanDisk cards in the DR680MKII recorder with no problems.
I started with a 64 GB card that is no longer available in the US:
SanDisk 64GB ExtremePro Class 10 UHS-I U3 SDXC Memory Card
MFR: SDSDXP-064G-A46
Back in May, I bought a pair of these:
SanDisk Extreme PRO 128GB UHS-I Class 10 U3 V30 SDXC Memory Card
MFR: SDSDXXG-128G-ANCIN
I generally do a full format of the card before starting a new recording session. However, I recently taped for 4 days straight at a festival with two recorders. The 128 GB cards were mostly filled by the end of the weekend. I backed up the data onto a hard drive each morning for safe keeping, but didn't delete them from the card. As I said, I had no problems. Knock on wood!