The Tektronix Type B is a plug-in for 500-series scopes.
It is identical to Type A, with the addition of a ×10-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.
The military version is known as the AM-1841/USM, wich is the same as a 53/54B MOD601.
K, L, and T are tied for longest production life, at 16 years.
B, D, and G are next at 15 years.
Lavoie Laboratories produced an unauthorized clone, the Lavoie LA-265-B.
Schematic of early version
Schematic of late version