I have my Tefillin and Mezuzot checked regularly (by a qualified Sofer). But how is it possible to determine whether Sta”m was written with the proper Kavannot (at the time)? Also, with respect to Tefillin, how does one know if it was written Kesidran?
You are bringing up a good point. We can’t know (unless you have ruach hakodesh etc.) what was in the sofers mind when he wrote the Sta”m. this is why it is important when buying sta”m that it was done by someone that has yiras shomayim, because essentially we have to trust the person, and his yiras shomayim for the tefillin’s kashrus.