The Tektronix Type N is a sampling plug-in introduced in 1960 for 500-series scopes. It was the first sampler produced by Tektronix. The risetime is specified to be under 600 picoseconds. The Type N is a complete sampling subsystem, using the 500-series oscilloscope just as a power supply and a display. The oscilloscope is operated in X-Y mode and gets its horizontal signal from the Type N plug-in instead of from the scope's sweep circuitry. The input connector is a 50-ohm GR-874. The Type N was introduced in 1960, followed by the 661 a year later, and discontinued in 1964, making it the shortest-lived plugin.
The manual (without schematics) is here:
The schematics are here:
Factory Calibration procedure: