I have an early serial # yss-62 and agree that the intonation is next to perfect, compared to other sopranos. Took me a while to tune my chops, but the horn is absolutely the best.I have both a Yamaha YSS-62 and the bent neck YSS-62R. The 62Rs were indeed factory production models. You can buy a nice 62 for about USD 2,000+, but the 62Rs are now selling well in excess of USD 3,000. They sound the same to me, but having the bent neck is a real positive because you can put some weight on the neck strap and the angle is more comfortable for play. Other than the bent neck and a slight change in the octave mechanism to accomodate the bent neck, the horns are identical and sound the same to me.
As I final note, these are stunningly good horns in terms of intonation, ergos and speed. All notes speak easily and the dynamic range is fabulous. I highly recommend either of these models.