Greetings Jon & all,
Not familiar with a CX 630, might we be considering an SX 630? Here is a circa 1983 or 1984 Simplex Catalogue which I had scanned and uploaded in its entirety.
One SX 630 model shown on page 8 and another variant with a longer cage on page 12.
A useful source of info on later era Simplex derailleurs, these pages give details of the recommended cog and chainring sizes and the total chain wrap capacity. Within the different groups (referred to as bronze, silver, gold - which were essentially quality & price point distinctions), you can better distinguish from the photos the differences between the sometimes quite similar models, but often with surprisingly dissimilar gear ranges.
These were the "final" evolutions of many late Simplex derailleurs. Many models were definitely little changed from the late 1970s models. I suspect all worked pretty nicely... but, by this era Shimano was also producing a wide selection of derailleurs as well... which were probably just as good, or better, and maybe a bit cheaper than the best of the Simplex derailleurs.
I noticed in an early 1980s Motobecane catalogue that the Team Champion was using the Super LJ 6600 with a tri-color "M" logo added right beside the Simplex script on the outer parallelogram plate, so they were still highly regarded... at least for the French domestic market, where they would also have been competitively priced against other imported marques.
Many of these derailleurs may still be good values, priced far below the exalted market prices of the earlier 1970s models, so these pages may be worth downloading and saving in your PC files... especially if you are a Francophile bargain hunter and could benefit from a "field guide" to help distinguish between the ranges and features of all these models.
BOB HANSON, ALBUQUERQUE, NEW MEXICO, USA
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