What a great haul! The chap you got them from obviously liked that handle. While not absolutely right due to the handle, the Streamline is still an excellent shave whatever it sits on.
You spotted subtle differences in the font and placement of the words on the 1912s. It's a real puzzle and a lot of fun to those of us who are addicted to 1912s.
Are some of the handles lighter than others? From the pictures it looks like you have some of the older heavy handles and some newer light aluminium.
In all, you've got a cracking set there. Enjoy them!
I also see you bough the Cussons pot. I saw one online and considered making a bit. I bought a Dubarry Bakelite instead.
Enjoy!