It's really weird how much these Simplex derailleurs arepriced so high as they dont have the "polish" of their competitiors. A contemporary derailleur, the Cyclone MkII, (which are presently going for under half the price of the Simplex) seems to be a much better deal than a SLJ6600 any day if you place them side by side or compare their shifting performance, I also suspect that the Cyclone would be a bit lighter than the Simplex plus, the Cyclone seems to also be a more sophisticated design with all it's allen head bolts and very compact dimensions. I especailly love the way Suntour cleverly routes the control cable anchor between the parallel arms instead of the more typical outboard mounting that Simplex and Shimano uses. But I guess, in the end, the Simplex will always win when you need that French finishing touch to a top end French classic bike you might be building.
It's just the idiosyncracies we deal with when restoring classic and vintage bikes.
Come to think of it, I should really buy myself a couple of NOS Cyclone MkIIs when they come up, before everyone realizes just how fantastic a derailleur it is........now that I can't afford Super LJs and SLJ660s anymore.....
Chombi