The build date on my 92 is july and this is the transmission I have you were so kind enough to post.
On the right side Ahead of the secondary oil pump Is the B2 servo , ahead of that is the B1.
I have a transmission from a 1990 300d which has no forward or reverse and the B2 servo cylindrical cover took everything I had to push in, and did not return against the outer lock, I was trying to find a comparison.
Back to my transmission , The cylindrical disk on my B2 pushed in so easily and just barely returned to the outer lock without any real psi but the return psi maybe is not what seals the cover because the seal is behind the cover if I am reading this picture right part 364.
http://www.ganzeboom.net/images1/ganzeboom/parts/Mercedes/722.3,%20722.4.pdf
JamesDean thanks for this.