This is only a short history of the M7. (For additional info, check some of the Microtech Gefell sites.)
The M7's history, design and description is a bit confusing, because neither Neumann/Berlin nor Neumann/Gefell ever bothered to trademark the capsule. So now several manufacturers freely use the term "M7" without necessarily much regard for authenticity towards the original M7's features, dimensions or materials.
Today, Microtech Gefell (one of the original M7 manufacturers-the other being the old Neumann company which had relations during WWII and after with today's Gefell company and location) and various international capsule manufacturers make capsules that look but don;t necessarily perform, like an original M7 capsule.
1. The original (Neumann East/West/Gefell) M7 capsule made with PVC diaphragms (ca. 8-10