Most new accordions sold here are made in china, they often have Italian sounding names. In my years repairing accordions I have yet to run across a Chinese instrument that did not need some adjustment.
 Accordions are incredibly complex instruments inside, and corners are cut to keep the price low. Some brands are better than others - but the quality at best is inconsistent.
 Used instruments are a gamble if you buy them from someone who does not either play or repair them. Ask lots of questions. How the instrument was stored over the years will have a big effect on condition. dampness will cause mildew ,but even worse is rust. Rust will seriously affect tuning, and is costly to remove. Heat can dry out the leather valves,dampness will mildew them. Bad valves will often produce a gargling sound ,or a sort of pop as a curled leather snaps into place from air pressure. Leather valves have a lifespan of about 30-50 yrs.    Nearly all Chinese instruments use poorly tanned leather ,and often several will be bad right out of the box, you will get what you pay for. Some of the better Chinese ,and almost all modern European instruments use Mylar and Mylar/leather combo valves.
 The reeds are held in with a bees-wax and rosin mix. Instruments stored in hot places can have the reeds melted right out of the holders. This wax gets hard over the years also, and can allow the reeds to move and cause tuning problems, this is often produces a metalic buzz when the reed is played. The wax has a lifespan of 25-60 yrs. It is hard to find these problems unless you know how to look for them, and often involves dissasembly of the instrument. Plan on having any used instrument serviced before it will sound really good.