I hope I am not opening a discussion that has already been made (I don't seem to have found it..), and that you will forgive me if I ask questions that might seem trivial to you.
The first one that comes to mind is about the wood used for the soundboard: is the one from the New York factory American or is it imported from Germany? Regarding the action, I have had the opportunity to see that there are slight differences in the shape of the agraffes and the repetitions - if I remember correctly, also in the size of the repetitions (repetition levers) -. It also seems that the hammers are more heavily felted (philosophies likely dictated by the jazz climate of the USA). How much do these differences actually affect the touch and how?
Asking in the United States, they told me that Horowitz used S&S from New York for his concerts (however, I don't trust them, it could be an attempt to claim their own nationality, so I am asking you). Apparently, the furniture finish was slightly more matte (but this might mean nothing, since in both New York and Hamburg Steinway can produce finishes to customer order).
The woods of the soundboard seem to me to come from Val di Fiemme, the famous spruce... For the rest, I am not a technician, so let's wait for the intervention of the others.
Pianos are almost identical except for the hammer tone building; the Nevesi hammers are made in-house and are born less compressed, with an elongated shape, and are voiced through subsequent impregnation on different areas and with different densities. There are also some different adjustments in the action: the accelerated action used by Americans, which features a bump instead of the Rosette on the center point; they probably also maintained the capstans with an inclined heel as was the case for all American Steinways until the 60s...
In Hamburg, the hammer is decompressed with puncturing, so through a reverse procedure....
It is unknown where the woods come from; the soundboards seem Canadian to me in both cases, as for the wood of the panels I do not know (the department cannot even be visited).
For me, overall, these are minimal differences, even in the cabinetry; the models are the same, one just needs to know how to choose in both cases.
