As usual Quercetti toys are excellent quality, which I suppose is only natural since they're made in Italy and not in China. When assembled gears stay in place and not wobble or come apart as you might expect. My 3.5 year old can put it all together himself, so perhaps it is save to say it is 3+. The price is a steal for Italian toy, it is pricier on eBay. Colours are very good as well, bright but not excessively so, very clear and pleasant.
What I believe is missing of making this a 5-start toy: - a container for the pegs (or maybe forgo them altogether as they're largely decorational) - one of the gears to have a dial and also for there to be ab arm of some sort to give kids a idea how different gears affect the motion of the arm in time. This would be more educational.