The Tektronix 7B50 is a timebase plug-in for 7000-series scopes, particularly the 7500 series. It is specified for triggering up to 100 MHz. Triggering uses tunnel diodes. The sweep is fully discrete, no ICs. There is a 7B50 and a 7B50A.
The 7B50 has a dedicated switch to put it in "amplifier mode" for X-Y operation. In this mode, the Trigger Source switch controls the signal source – internal from a vertical plug-in via the trigger path, or external — and the Trigger Coupling switch controls AC vs. DC coupling. In amplifier mode, gain can be varied using an uncalibrated potentiometer.