U1 系列在日本，在别的地产的型号不一样。在yamaha 网站上弄来的介绍

Yamaha Pianos produced for the U.S. market have been manufactured in 4 locations:

Hamamatsu, Japan Thomaston, Georgia South Haven, Michigan Jakarta, Indonesia

As a result, there are four different serial number ranges for Yamaha pianos. If the serial number begins with a "T", the piano was manufactured in Thomaston, Georgia. If your grand piano is a GH1G, GH1FP, GC1G, or GC1FP, your piano was manufactured in Thomaston, Georgia. If the serial number begins with a "U", the piano was manufactured in South Haven, Michigan. If your grand piano is a GA1E, DGA1E, GB1, or DGB1, your piano was manufactured in Jakarta, Indonesia. If your piano is any other grand piano it was manufactured in Hamamatsu, Japan. If your upright piano is taller than 45" it was manufactured in Hamamatsu, Japan. If your upright piano is 45" or shorter and has seven numbers in the serial number, it was manufactured in Hamamatsu, Japan after January, 1970.