Dave Porritt, Thank you for your extensive input . The fact that the Steinways considered the duplex of great importance is evidenced by their catalogue in the 1874 Philadelphia Convention.They listed ten features their new piano included. The duplex scale was the second. Not only that but the name duplex scale was cast into the plate for many years with the serial number. In addition there is significant correspondence between Steinway and Weber showing that Steinway considered Weber's attempt to use his patent a serious breach of ethics. If this is subject important enough to you and you can not find this catalogue , I'll be glad to try and dig it out of my records. Dan Franklin
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