Thanks for your answer!I agree that normally $400 would be a fair market price, for an accordion with those apparent specs. I do suspect this possibly may be a slightly more premium build than the standard 2/4 reduced size instrument and newer (with more useful life left) than many of the instruments in that category that are oversaturating the market and driving down the value. They don’t list reed types in the listing and pictures aren’t very clear but this may have Tipo a Mano reeds and may be the exact right instrument for student that needs a no nonsense reduced size accordion.
The question is how well this has been maintained and if it’s the accordion you need. A 16.5” 41 key keyboard is too small for many adults to play comfortably. If it’s the right accordion it might be the kind of instrument that is worth paying a bit more for.
I can’t speak about Guerrini particularly but I expect it’s about 99% likely that this is stencil brand built by one of the builders in and around Castelfidardo.The register buttons look like Guerrini to me, maybe it's just rebranded?