Jan van Geelen his maker's mark; dove in a circle. The maker’s mark on the piano appears to be a swan, not a dove, without circular cartouche. The piano has no Dutch guild city mark or any other valid Dutch hallmarks. I believe it to be pseudo/fake marks and perhaps made recently.
Thank you oel. Probaly German silver Alloy. It was highly oxidized like 800 silver. The swan does not look like J. Kurz or Scleissners Hanau marks. The N looks similar to Gebruder Gutgesells however he does not show swan mark. I will try to research further or someone else may know maker.