I’ve voted once again, this time in your new poll, as also did for the first one.
I was guessing the trem no. 2 was the FR and I was right, as mass matters for sustain, because or inaertia (inaertial mass is just important for a “loose”, floating bridge system, which a tremolo, correct name vibrato, is at last).

And once again, my vote was within the majority choice, and I believe that final results will not change the order we have now.
But you challenged a bit further this time, then my guess is:

Block 1 – aluminium
Block 2 – brass
Block 3 – steel

I may be wrong, but this is what my ears are telling me, due to timbral features of each sound, also bandwidth associated with sustain and level perceived in the samples.

Anyway, there is still a phenomena that could spoil all these suppositions:
If you drop a 1€ or 2€ coin onto a hard floor (ceramic tile or stone), what kind of sound do you get? Not the one you could expect out of a 100% brass coin, nor out of a 100% nickel coin, despite these coins are composed of two pieces, one of each metal.
It rather sounds like you’ve dropped a piece of aluminium, isn’t it?

What happens, is that different ressonant metals do mute each other in some extent, when attached together and put vibrating.
They do not ressonate at the same frequency nor with the same timbre, which makes them to cancel some of each other’s frequencies and harmonics, and get quit very shortly after the sound peak.
This is also a principle used by turntable makers (once again to obtain quite neutral, “dead” platters by making these out of different material layers in a sandwich fashion.

But here you don’t want to cancel vibration, nor frequencies, nor harmonics, but just the opposite, you want them all to last and expand.
So much care have to be put when “marrying” metals and you’re just going the right way by experimenting.

Even thought that your biggest enemy will always be the aimed featherweight and at some point you may have to allow for some extra grams for timbral, harmonics and sustain sake, nevertheless also metal ressonance compability matters in a good extent too.
I’ll keep waiting for the final results of the second poll, just to see if my guesses are right.

All the best and kindest regards,

José Paulo