[cyblord]

The Greek letter 'mu' designation (i.e., what you referred to as "u" in the model #) is unknown to most people. My understanding (but I'm kind of guessing) is that Yanagisawa uses this designation when they update a model, but not sufficiently to warrant an entirely new model #.
For example, I once owned a 990u tenor, which seemed to be a model newer than a 990 but was made before the 991 model name was introduced.

So the 990u is an updated version of the 990, but not quite the 991?

In that case, should a 990u be worth more than a 990 consider that they have the same condition?

Thanks!

 

[Hurling Frootmig]

The 990u has some toneholes that were placed differently to improve intonation. It looks like the 991 further refined the placement.