It’s been floating around the internet for the last 10+ years. No idea where it came from.

 

I downloaded an "official" Audi service manual, from emanuals online but while it covers technical details fairly well there are no accurate photos and I'm still in the dark on how to get a brake master cylinder completely removed from a 1998 Audi A4 Quattro. I know I need to remove the fitting from the cylinder and the slave, but it looks like it has a rather strange nut on it and I don't want to try it with a hex wrench if that is the wrong thing to do.

 

This is from a B6. Does this help?

https://www.pelicanparts.com/techart...d_Resevoir.htm