Yanagisawa A4 Alto saxophone
The Yanagisawa A4 alto saxophone is considered Yanagisawa's first semi-professional instrument. They were built from 1966 to the mid-1970s. There is not too much information online about these saxes, but I have collected this and supplemented it with my own observations.
The A4 was built under various names and does not yet have a Yanagisawa designation on the cup, but the Yanagisawa logo is always stamped under the serial number. At the time, they were produced under the name Whitehall, Astro or Dorado. So these are not so-called stencils: the Yanagisawa logo appeared on the cup around 1980. All these saxes are hand-built in Japan and of high quality.
The A4 (and T4) are easy to recognize and differ from their successors A5, which are based more on Selmer keywork. Low B and Bb keys have a different mechanism, the left little finger plateau is different, the pants guard is missing, metal thumb rest, no high F-sharp, different shape of right F-sharp key and (most importantly) a completely different bore. The neck opening diameter is 25.5 mm, instead of the standard 24.7 mm. This makes for a more dark and centered sound.