I obtained this mysterious derailleur from Italy - so I am guessing that it is Italian.

An Italian reader of this site, who has proven correct in the past, suggested that it might date from early in the Second World War - when the Simplex Champion du Monde derailleur was very popular in Italy - but supplies were difficult to obtain. His contention was that a number of small Italian manufacturers may have produced derivative designs at this time. He also thought that this might also explain the slightly weird finish and lack of branding. This is all good, except this derailleur displays a number of original and complex design details - surely a straight copy would have been a more usual response to 'supply chain issues'? Despite this, based on my correspondents opinion, I have given it a date of 1940.

It has some very particular features:

• There is no branding anywhere - only the number '1' stamped on the main arm.
• The main cylinder, along which the pulley wheel slides, is welded into the main arm, or perhaps is even cast as one piece with the main arm.
• The construction of the pulley wheel owes much more to a Super Champion Champion du Monde than it does to a Simplex Champion du Monde.
• The pulley cage plates have a distinctive devilishly flared top.
• There is something clever but incomprehensible going on with the pulley cage movement. The range limiting bar does not fit into a round hole in the main arm. Instead it is mounted in a slot that allows some adustment forwards and backwards. Also the sleeve that carries the pulley and pulley cage plates has two spiral slots in it that engage with pins on the component that carries the cable nipple, implying that the pulley cage plates are meant to rotate in some way at some point.
• This example has a chain tension spring that pushes on the front edge of the main arm - much as in a Simplex. However there is also a raised protrusion on the back of the main arm with a slot in it that looks to be designed to accept a spring. Perhaps the spring and/or hanger plate are not original.
• And finally there is the issue of the cable routing. On the face of it it looks as though a nipple should be held by a nicely shaped piece on the inside of the pulley wheel mounting assembly. The inner cable should then run along inside the cylinder and out through the small hole in the face of main arm, passing into outer cable at the point that it emerges, All very neat and typical of Italian derailleurs of the time. However there is also an outer cable stop cast onto the main arm (near the top). How is this all supposed to work? Is something missing?

Deeply mysterious and interesting. If anyone knows anything about this fine derailleur, please let me know.

• Derailleur brands: Unknown Italian
• Country: Italy
• Date of introduction: 1940?
• Date of this example: unknown
• Model no.: unknown
• Weight: 240g excluding droput bolt and the broken part of the pulley cage
• Maximum cog: 22 teeth?
• Total capacity: 8 teeth?
• Pulley centre to centre: none
• Index compatibility: friction
• Chain width: unknown
• Logic: low normal
• B pivot: sprung
• P pivot: none
• Materials: steel