I saw these numbers printed on to the piano:
900
19
And this letter and number written on the wood below the keys (possibly in pencil):
R 6418 (or 6478, not too sure)
There is also a logo, which is a slightly rectangular box with the letters FS (?) in it. What could this logo be?
I can't seem to upload a photo of these numbers and the logo, but I'll try.
更新1:
*I saw the numbers 900 and 19 printed inside the piano.