The Tektronix Type B is a plug-in for 500-series scopes.
It is identical to Type A, with the addition of a 10x-gain
AC amplifier which can be switched in to extend the vertical
sensitivity from 50 mV/div to 5 mV/div.
Like the Type A, the Type B has its roots in the 1954
introduction of the 531 and 535, as the Type 53B,
with 10x-AC bandwidth of 2 Hz to 9 MHz.
In 1956, it was replaced by the Type 53/54B with DC-20 MHz
or 2 Hz-12 MHz bandwidth in the 541 and 545.
In 1959, the Type 53/54B was renamed the Type B,
and it was available through 1970, a seventeen-year run in all.
Lavoie Laboratories produced an unauthorized clone, the Lavoie LA-265-B.
Schematic of Early Version
Schematic of Late Version