When I wrote about wanting a longer stem on one of my bikes, several people suggested I get ahold of a vintage adjustable stem. I did not know that such a thing existed, but clearly there is much I don't know.
Long story short, I am now in the temporary possession of a 3ttt Record Regolabile adjustable stem, on loan courtesy of Jan Heine of the Bicycle Quarterly. I decided to use it not on my own bike, but on the Royal H. randonneur collaboration - it just looked so appropriate.
Produced in the 1970s by Tecno Tubo Torino of Italy, this elegant stem adjusts from (I think) 6 cm to 12 cm. Here is more information about it and some close-up pictures. The beauty of this system is that it combines the vertical adjustability of the quill stem with the horizontal adjustability of the threadless stem (with the latter you can swap out stems without redoing your handlebar set-up). Why are things like this not being made anymore? Those of us who constantly change our minds about handlebar positions would find it extremely useful. Right now I have it adjusted for 8 cm, but who knows what the future holds - I am looking forward to playing around with this!