I teach the piano to primary school children and bought this metronome as an alternative to the electronic ones. In this computer age, children find the mechanical movement and sound more engaging than the beep of yet another electronic device.
Though the case is entirely plastic it's resilient enough for the metronome to be carried to and from school in a box of books, so long as you're careful with the winder on the side. It doesn't come with any bag, though, so needs to be wrapped up to avoid scratches to the gloss finish.
The clicking sound is stronger and richer than you might expect -- just as loud as wooden equivalents I've used, though with a slightly different tone. The tempo adjustment works in the conventional way (governed by the laws of physics): like most mechanical metronomes, it's not great for accurately setting very slow tempi.
I took it apart to look at the works and the parts look fairly fragile with the main cogs and clicking wheel made from plastic: as you'd expect for the price, it's not really a precision instrument. So far, though, it's proven itself to be good enough to do the job required.