This ZZR is a carbon copy of a Simplex Juy-51 - a design that uses two cables - one to tension the spring. This ZZR has all the Simplex features including the legendary ‘Get-You-Home patented gear selector’, that allowed you to trap the toggle chain if the cable snapped.
However the most amazing feature of this derailleur is that the earliest record that I have found of its existence is a Romet instruction book from 1971. It is also conspicuously missing from all earlier Polish instruction books, the latest of which that I have seen, dates from 1967. This seems to imply that this 1951 design, that had been unquestionably obsolete since 1961, was actually introduced into the Polish market after 1967, and possibly as late as 1971. Helpfully, Google Translator gives the Polish translation of ‘time warp’ as ‘time warp’.
I have photographed this example with the top knuckle spring disengaged - to allow the derailleur to take up a more normal position.
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