Neumann used two capsules as original equipment in commercially available U47 (tube) microphones:
First the M7, from 1948/9 to ca. late 1959, and thereafter the K47/49. The latter was also used in the U47fet (and is still used in the M149, and M147.)
The K47 was also used since 1960 as replacement capsule, when a U47 with defective M7 came in to Neumann repair facilities.
The "M48" you mentioned was the KM53 small diaphragm omni capsule installed in the short-lived Philips (U47p) model (ca. 1954 to 1955). It had detachable (bajonet) heads equipped with M7 or K53 capsules.