Fantastic collection Nick, i think my favourite would have to be the Stuart one-one which i had the pleasure of steaming a few years ago.
Yes, one of my favorites as well! Here is your video of the one-one
And here is my noisy airbrush compressor test run
I'm very surprised you let that mint boxed factory finished Stuart S50 go! 
I was up to four S-50's, so one had to go... I have two early round cranks and a good running later example that I want to add a governor to. That NIB model was too nice for me to modify and sat on the shelf for many years un-used.