The 32 series horns are Yamaha's semi-pro or intermediate horns which I believe are now superseded by the 475 series. In the US the 32 series was called the 52 series (I think they may have been made/assembled/built at Yamaha's Grand Rapids, Michigan complex). Prior to the 32 series was the fairly rare 31 series horns.
I have never heard of the 40 or fity (50?) series horns. Early Yamaha pro horns were the 61 series which become the 62 series, and then in the late 1980s, early 1990s the Custom 855 (alto only) and Custom 875 (alto, soprano and tenor) were added to the range and now the more recent Custom 82Z, and the variants of the 875 range.
The 21, 23 and 25 series horns were student horns now superseded by the 275 series; 31 and 32 semi-pro horns now superseded by the 475 series; 61 and 62 series now superseded by the 62II series; and the more flashier pro horns Custom 855 (alto only now discontinued) Custom 875 with various suffix EX, ET, EZ, EY? and the Custom 82Z.
And to top it all off in NZ we have the Q series horns and the AS100 and TS100 series which are another range of student Yamahas.
Gets very confusing.
Regards,
Greg Strange.
P.S. The first issue of Saxophone Journal magazine I ever purchased was from Tower Records (Regent Street/Picadilly area) in London in the early 1990s, one of interviews was with UK classical sax player Paul Harvey (Kneller Hall, London Philharmonic) and his tenor sax of choice was a Yamaha YTS32.