The Patent process isn't overnight and immediate. Hope that answers your question.
As I stated in your other post. The poor rib structure and thin panel is the source of the sustain problem in your Steinway. Plus Steinway usually placed a heavy load up in the treble compounding the problem. Check the thickness of the soundboard in the top nosebolt hole. In most other high quality pianos that would be near 3/8"- thick, but in the diaphragmatic board its closer to 1/4"+ thick. That's a problem for the second section (weak octave area).
Hi Chris - I checked the web and also other posts on this site, and it seems to be very consistently presented that diaphragmatic soundboard was NOT used until the mid 1930's - patent lodged 1935 and granted 1936.
As regards thickness of my soundboard, I measured the following at the nose bolts holes :
0.345" each for the two on the far left of the frame on the base strut (see photo of piano in the link in previous post, where you can especially see the location of the lower bass strut bolt in case not familiar)
0.34" at the tenor side nose bolt, and 0.36" for the treble side. Note this was a little tricky to measure, (using a bent piece of wire poked through the hole and marked with a felt pen from underneath) - so overall I would say all four holes measured the same.
According to Steinway website, the board should indeed be around 9mm/0.35" in the middle/apex of the crown, tapering to 6mm/0.24" at the edge, as you indicated. Using the actual patent diagram as a guide, the thickness at treble plate bolt should be around 20% of the taper less than the tenor one - which is only 0.023" and not viable to measure with my low precision measurement method, noting that the treble one was measured as 0.020 thicker. I think the most telling measurement though is the lower bolt on the base strut - it is only 5" from the rim and has NO taper compared to any of the other three, whilst I would estimate from the patent diagram, that this measurement should exhibit it lease 80% of the taper. It would therefore appear that my sound board is NOT of the diaphragmatic/tapered type.