I believe that is a CA “CARB” sticker.
These are incredibly valuable (think $10k+ to CA buyers) on old imported G-wagons with engine swaps to ensure they can be easily registered/plated in CA.
The odd thing is that this car should be old enough to be grandfathered in, and therefore not need a CARB sticker to qualify. The CARB approval process is a PITA, takes months to complete, and is very expensive.
RE: pictures
Seller, if you’re reading this thread, immediately find a competent local photographer and pay them $300-500 for a quality photo shoot. I guarantee you it will return 10x that amount in your final hammer price!
Pretty car, GLWA!