465M
The 465M is essentially a 100MHz bandwidth scope in a the cabinet of a 455. 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. In theory, this gives the 465M a 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 or single timebase module made, although some may have been originally on the drawing board.
Whether or not the 465M was more rugged than the original 465 is unknown. In the Oklahoma City Tektronix Service Center, a lot of 465Ms came in for warranty service, primarily from the Federal Aviation Administration which had purchased a large quantity of that model. But the rate at which instruments are brought to a service center is not by itself a measure of reliability, as one would be comparing the failure rate of a large number of new 465Ms that were shipped to the customer's depot with an established base of 465s which already had most early defects corrected.
