The 155-0178-00 (H488) is a Tek-made horizontal output amplifier implemented as a thin-film ceramic hybrid in a custom "Hypcon" package.
It has an input impedance of 50 Ω per side and is designed to operate into a 365 Ω differential load. It has a current gain of 3.3 and is not back terminated.
The device uses T-coils at the input and inductive peaking at the output. Its rise time is approximately 0.5 ns.