I just wanted to point out that the TLM 49 is a single-pattern cardioid microphone, like the M 147 Tube and the U 47 fet. In those models the back half of the capsule has a purely acoustical function, and no electrical connection is required.
From a practical perspective, a dual-diaphragm capsule for a single-pattern cardioid microphone doesn't need to meet any very high standard for front/back response symmetry. It's mainly in the figure-8 setting that this matters (since any difference in front/back sensitivity causes the null to deviate from 90 degrees, thus making the microphone unsuitable for M/S or Blumlein stereo recording).
I don't know Neumann's current practices--they've gone through several twists and turns--but for some years at least, K 47/49-type capsules for single-pattern microphones were finished, QC'ed and stocked separately from the capsules for their switchable-pattern models. Unfortunately, the naming conventions have also varied over the years. As a result, the name printed on the box doesn't necessarily tell you everything that you need to know. It could take some extra effort to find out for certain what a given capsule actually is.
--best regards