i have three of those radios. they are all very accurate but i think
that you are just lucky. the parts have a tolerance percentage that they
are manufactured to. this slight variation is probably compensated for
by an adjustment and is set by a guy on the production line to another
tolerance specification. nothing and no one is perfect, so if your radio
appears to be perfect then you can bet that you will soon drop it or
leave it in the sun too long or anything that might change things. even
storing it too close to strong electronic fields can affect the
accuracy. heck, they even had to compensate the atomic clock a few
seconds several years ago. (some nimrod will flame me and tell us
exactly how many nanoseconds it was) you just got an unusually tight
tolerance on your unit and that could evaporate as it ages.