I noticed that most boutique amps are some variation of either a Tweed or Blackface Fender. The Fender amps made from 1955 to 1965 are still considered the standard for judging other amps, Marshall's were first designed off of the tweed bassman. With the exception of Vox amps, Leo designed durable amps for the working musician that no only sounded good but held up to touring. Whatever Leo had that allowed him to design and produce those amps during that 10 year period was truly historic, and if you think about it he went from a relatively small company in 1955 to a large complex company in 1965 where they were doubling the output of products every few years yet the quality during that 10 year span was consistently very good. I would have loved to been present during some of their R&D sessions.