Yikes. The first thing you need to do is get in contact with the seller to figure out their take on the situation (re: What is the cause of the streaking? Why was it not disclosed?).
To me, it looks like a haphazard, DIY paint job. Based on the hardware, construction, stamping, etc., this a very old bag. I’m sure it was painted to hide cracking/dryness, as it’s next to impossible to find a bag of this vintage on the secondhand market without some form of cracking/dryness. That being said, if you wanted to make sure that it’s not just residue from a cleaning job, you could use a leather PH wipe (maybe check
@docride ’s thread for recommendations) to see if the residue goes away.
In the very likely case that this
is a botched paint job, Hermès will definitely not accept the bag to Spa. In that case, if you decide you still want the bag, there are many third-party services who may be willing to work on your bag. Best of luck!