Shimano Tourist Speed derailleur

When it comes to the range of Shimano's mid-1950s pull-chain derailleurs I am, largely, operating in the dark. I have never seen a contemporary catalogue, advert or even a set of fitting instructions. The gloom is dimly lit by Hideki Sasaki's heroically excellent 'Derailleurs of the World - Shimano', but I still have more questions than answers.

My best guesses go something like this:

In the mid-1950s the dominant derailleur in the world was the Simplex Tour de France. In Japan the dominant derailleurs were the Sanko S series (which were not unrelated to the Simplex Tour de France.
By 1955 there were a number of enthusiastic manufacturers active in the Japanese derailleur market. Shimano's 1956 entry was relatively late and perhaps a bit reluctant. Shimano's main focus may have been on its brand new three-speed hub gear.
When, in 1956, Shimano finally did decide to launch a range of derailleurs, their designs were heavily influenced by the Sanko S series and the Simplex Tour de France. As with the Sanko S series, Shimano developed a pull-chain, sliding rod, mechanism and deployed it across a range of derailleurs with different mounting systems and different pulley cage lengths.
I believe that, in 1956, there were initially two models, an axle fitting 'racing' model with a sprung b-pivot and a short pulley cage, and a chainstay fitting 'utility model' with no b-pivot and a medium length pulley cage. Neither model had a cable adjuster. Both models were called 'Shimano 3.3.3.'.
In 1957, I think that the range was redesigned and rechristened. The axle fitting model lost its sprung b-pivot and gained a, slightly redesigned, mid-length pulley cage and a cable adjuster. The chainstay fitting model was restyled, and also acquired the slightly redesigned, mid-length pulley cage and a cable adjuster. I believe that both were called 'Champion Speed'.
At some point a long cage derailleur was introduced. There is some evidence that, also at some point, this was called the 'Tourist Speed'.

These were well made derailleurs, with good chrome and accurate small parts. But they were very derivative and devoid of any original thought. It would be another ten years before Shimano really got interested in derailleurs.

This is a, richly chromed, unused, example of a Shimano Tourist Speed. Very nice it is too. Unlike other Shimano derailleurs of the period, chain tension is supplied by a spring running underneath the chain stay that hooks into the eye on the top of the outer pulley cage plate.

This derailleur has the following features:

It mounts on a braze-on under the chainstay.
It has no b-pivot.
It does not have a cable adjuster.
The, long, 70mm, pulley cage is rather similar to pulley cages used on Simplex and Huret touring derailleurs.
The pulley wheels are black, notably symmetrical and have adjustable threaded cones.

This is a confusing model. The lack of cable adjuster and pulley wheels with threaded cones point to it being an early (1956?) model. The shape of the main arm and the black colour of the pulley wheels indicate that it is a later model. I have not seen the beautiful, highly chromed, finish and symmetrical pulley wheels on any other Shimano derailleur. It's a mystery.