This is a fascinating, confusing and frustrating derailleur. I will try to breakdown the elements of its design:
- The knuckles and pulley cage parts are from the very first (1978) style of Shimano Dura-Ace EX (7200).
- The inner parallelogram plate is similar to that of a Shimano Dura-Ace EX (7200) - but with no lettering on it.
- Both pulley wheels have stainless steel teeth. A Shimano Dura-Ace EX (7200) only has these teeth on the guide pulley.
But also:
- The cable clamp and outer pulley cage plate incorporate a 'Centeron' lever - that is rather similar to the one on a 1981 Shimano Deore (DE10), except that it is aluminium.
- The cable adjuster is more similar to that on a Shimano Deore (DE10) than that on a Shimano Dura-Ace EX (7200).
- The large Allen key b-pivot and p-pivot bolts are unbranded and manufactured from aluminium, unlike the branded steel bolts on a Shimano Dura-Ace EX (7200). This may be to save the weight that the Centeron lever has added.
- The parallelogram does NOT have alignment pins in two pivots as these would serve no function, given the presence of the Centeron lever.
So what is this derailleur? The high quality of the detailing on the outer pulley cage plate and on the Centeron lever make me think it is a genuine Shimano prototype. However the low quality of the riveting of the main parallelogram pivots starts to unsettle my confidence. Most baffling of all is the fact that this derailleur appears to have covered more than a few miles - as though someone had fitted it on a hack bike and given it a good thrashing.
It would have been extremely logical for Shimano to have developed the Shimano Dura-Ace EX (7200) by fitting a Centeron lever. If they had not been seduced by the cult of aerodynamics, this derailleur might very well have been what the Shimano Dura-Ace (7300) would have looked like. It certainly makes for a much more understandable bridge between the Shimano Dura-Ace (7200) and the Shimano Dura-Ace (7400).
I love it for its tantalising air of mystery.
- Derailleur brands: Shimano
- Categories: Shimano - the Dura-Ace story
- Country: Japan
- Date of introduction: possibly 1979?
- Date of this example: unknown (no two letter date code)
- Model no.: unknown
- Weight: 193g
- Maximum cog: 26 teeth (source: Shimano)
- Total capacity: 26 teeth (source: Shimano)
- Pulley centre to centre: 46mm
- Index compatibility: friction
- Chain width: 3/32”
- Logic: top normal
- B pivot: sprung
- P pivot: sprung
- Materials: aluminium, with stainless steel teeth on the pulley wheels