The Tektronix 465M is a 100 MHz dual-channel portable scope, the commercial version of the AN/USM 425 standard military scope.
It is essentially a 100 MHz bandwidth scope in the cabinet of a 455. A large user of the 465Ms was the Federal Aviation Administration.
The construction methods of the 455, 465M and the T900 series are similar. In contrast to typical 400-series portable scopes, which use socketed semiconductors, the 465M's semiconductors are soldered in place, giving it a theoretical reliability advantage.
The front panel layout of the 465M is nearly identical in appearance and function to that of the 465.
Since the vertical preamplifier and trigger/sweep unit are implemented as plug-in modules, one might guess that there would be other implementations of those functions, but there weren't - what you see is what was made.
There never was a single-channel vertical amplifier or a single timebase module made, although some may have been originally on the drawing board.
Whether or not the 465M was more reliable than the original 465 is unknown.