These are the first results:
Square wave of the HP8133A with the Tektronix sampling oscilloscope 11801C, x-axis 50ps / div, y-axis 200mV / div, with head SD26, rise time 17.5 ps, bandwidth 20 GHz.
200 ps wide pulse of the HP8133A with the Tektronix Sampling oscilloscope 11801C, x-axis 50ps / div, y-axis 200mV / div, with head SD26, rise time 17.5 ps, bandwidth 20 GHz.
The displayed rise time is about 50 ps in both cases.