The dials don't have limits, so if it's been upended in transit, their needles can cross over and jam together. I easily prised the cover off and freed the needles. I calibrated it to 4d celsius by leaving it in the fridge and turning the dial by hand, and 100% humidity with a damp cloth as directed. Be quick calibrating, the dials react quickly.
It now works as it should, and is fairly accurate. It's 70.5 x 26mm including the dome. It's designed to mount on a wall, where it looks good and is easy to read. By design it should be kept upright, so I wouldn't travel with it.