For Jethro Tull -

I also have a 1991 W126 model and it has only one air bag;
the driver's position. I have seen both examples of the W126,
some with one air bag only and others with both. I've no idea
what rhyme nor reason would dictate why one model gets
full air bag equipment yet another in the exact same model year
would not. Strange, considering it is a safety item.