I'm typing on the brand new F77! It is a great keyboard. Like I said with my F62 evaluation, these keyboards truly deserve the Model F moniker. The keypresses are very sharp and precise, as I'd imagine like a brand new original Model F would sound fresh out of the factory door in 1984, and maybe even a little better due to improvements in manufacturing and tolerances over the past few decades since the Model F's were introduced. There is noticeably less ringing/reverberation on these new prototypes compared to many of my original Model F keyboards, though there is still some musicality and different sounds with each key (though like I mentioned with my F62 evaluation, the keys are more consistent with each other in terms of their sound). I believe part of the reason for less ringing is the improved overall quality of the components which are able to take advantage of improvements in manufacturing accuracy, as well as the use of what I believe is a more dense, stable type of foam (the McMaster-Carr Neoprene/EDPM blend) as opposed to the less dense, disintegrating originals. Also I believe that a lot of the ringing is influenced by the condition of the foam and its relation to the top inner assembly (how tight/even the top inner assembly fits with the bottom inner assembly): the more disintegrated the foam, often the more ringing in general is what I've noticed.
I also tested the split right shift prototype and everything buckles well (though I am unable to test for the software of those two keys since I did not order prototype split right shift PCBs for either the F77 or F62).
The key will be my instructions to the factory regarding the quality control. I will ask them to test each key and make a video showing which keys sound good and which ones should have their springs replaced. For whatever reason about 10 of the springs (they sent me extra springs fortunately) did not pass my quality control. Maybe they were half a mm too tall (or stretched out a little).
A video will be forthcoming...
Thanks xondat. Those F62 photos were taken in my new light tent setup with softbox lighting.