The DME shows the circuitry for a O2 sensor. But the fuel quality switch looks unfamiliar like someone changed or repaired it. What is printed on top of the silver sticker on the chip?

It says TC 6000 on the silver sticker (if I'm reading in the right spot).

then it's a counterfeit copy of a old Weltmeister chip. Likely you have a working O2 sensor if everything is done right.

Thank you very much for the input Steve. Now I know to replace the O2 sensor as part of the maintenance of the vehicle. That was very helpful as that was the exact information I was looking for. If I need to repair this DME I'll know where to send it.