Is age a factor?

[Ralph & Frances Thorn]

Even a fine piano can present some unpleasant surprises.  An older
Yamaha with butt plates requires some extra service, and if
technicians miss this important detail a piano from the period before
1977 or so could require some extra work.

I assume that techs know how to determine the date of production of a
Yamaha?  In uprights the main rail, treble end top face has a long
production number printed - the first 2 numbers are the year of
construction.  Of course, if the rail is wood, it is 1967 or earlier.
As I recall, a similar number appears in grands, but not sure which
rail.  (long term or short term memory failing)  On uprights you just
look straight down inside, without taking off any case parts.  Quite
handy.

Ralph Thorn