We used to use the Genius 20+ years ago and they were fine to calibrate if they were slightly out of spec. We then moved to Braun PRO4000 and in then onto PRO6000. We have the test equipment and can verify the devices and any out of spec go back to Welch Allyn under our agreement.
A couple of years back during Covid we had to start using the Genius 3. We had some test equipment from the company but even in a small room at a stable temperature we had so many calibration errors they were taking up far too much of our time on this site. The requirements for calibration were changed to something impractical, possibly quarterly, at which point they were all swapped out for PRO6000.