Sight O Tuner

[PSFInc]

List,

We use a Hale Sight O Tuner in our rebuilding shop, they are great for
chipping pianos w/o the action. The other day we checked it against the
tuning fork and found it to be almost a half step flat. The Sight O tuner is
an older one and was recalibrated about ten years ago. I have to plead
ignorance in this case, is it possible for these to go flat like that and
how often should it be recalibrated? Is it perhaps another problem?

Thanks,

Ed Mashburn, RPT