Re: " I agree with pmansson. They are not seat covers, they are the factory velour seats. The piping you are seeing looks like a shadow. "
You are correct, these are shadows that I am seeing and not piping. Looking again at the pictures, this time enlarged, you are also correct in stating these are factory velour seat covers.
Apart from being velour, much of the look of these seats is lost without the heads rests, which (to me) are a signature design of BMW's of this era. All of this could be corrected with an order to World Upholstery, which is what I did to my '73 CS that had a velour interior from the factory as well.