The Tektronix Type O is a letter-series plug-in that contains two op-amps.
The input and feedback networks of the op-amps can be configured from the front panel using knobs and/or user-supplied components. There are sockets on the front panel for banana plugs.
Type O also has a regular signal input that does not involve the op-amps. A mode switch selects which op-amp's output will be displayed, or the regular signal input.
Regular signal bandwidth is 25 MHz, maximum sensitivity is 50 mV/div, op-amp gain-bandwidth product is 15 MHz, and open-loop DC gain is 2500.
Type O was introduced in mid-1962 and it was available right up to the discontinuance of the entire 500-series scope line in 1974.