It would be considered derogatory today to use the aptly descriptive "
Japanese Watts" of 1970s.
Looking at that X-101C advertisement, it is clear to me that Fisher was using that marketing-ploy long before the Japanese did... or had to.
"60Watt"? eh?
It's less "Japanese watts" than it is
pre-FTC '74 watts. The rise of transistorized amplifiers, commencing in the early 1960s, coincided with the IHF "music power" specification, which (from my latter-day perspective) rapidly devolved into... the Wild West in terms of output power claims.
Cf., e.g., this mid-60s Fisher 500C receiver (a longtime denizen in my basement, ultimately sent to a better place), still wearing its original power claim sticker:
Fisher backup 500C front by
Mark Hardy, on Flickr
"75 watts"

So, first of all, that is a stereo power claim; so divide by two: 37.5 wpc.

The 500C uses push-pull 7591A power pentodes in class AB (probably AB1). Realistically, probably 25 watts per channel continuous at reasonable THD levels (1960s vacuum tube "reasonable" levels, that is).
In fact, I
almost put a disclaimer in my earlier post about the pre-FTC '74 power claim... but there seems to be an interesting perspective held my many folks here that the "RMS"

--
ahem, I mean
continuous watt specification for output power is
un-necessary and irrelevant.
Some of us feel the need of honest specifications of amplifier output power according to acknowledged documents like FTC regulations and IEC standards. The reason is to get comparable data, protect potential customers and draw attention to false claims of some manufacturers.
I have decided to make such tests myself ad so far I have tested several well known amplifier and also one of my DIY designs. The links to the tests and results can be found below:
...
In full (and presumably unsurprising) disclosure, I am
not one of the folks holding that perspective, but that's not
knob/dial/switch related, so I'll stop there.

