The Shimano Positron 400 (DG-300) was a racy little number, with a dropped parallelogram, an aluminium rear knuckle and a short 46mm pulley cage. It had something of the look of the Shimano 600 (or rather its steel intensive brother - the Shimano 400).
However the geometry was noticeably different, with a distinct backwards slant on the rear knuckle - so that the rear sprung pivot is behind the parallelogram - the weight was even more distinctively different - and then there was that despicable piano wire...
Close, Colonel, but no cigar.
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