at this moment i don't know how is that possible, so to make the device trustfull
hello, it's been a while, but i believe i know how to check a genswiss system; idea behind it that any measuring device has to be checked to be within specs, and if it is ok, then you may use it without worries

is not enough to have a measuring device delivered with a certificate : a certificate means that it was ok when it left the manufacturer; whatever there is, periodical inspections are recomanded

the question, about a geswiss, is if the housing is cilindrical ( that is an easy check ), and if camera is coaxial with the housing :
... take a vmc, trammed, with a centro in it's spindle
... put a collet chuck on the table, with the genswiss in it
... find the center of the genswiss, then repeat near the bottom, so to be sure that it is coaxial with the spindle
... remove the centro, and put a center drill inside the spindle; check it, so to have low tir
... turn on the genswiss system, and rotate the spindle; pulse handle z, so to get it in focus : this will give you some numbers, because the vmc axis has positioning accuracy / kindly