they stopped making these chains...too labour intensive (apparently every chain link was checked my hand by his Dad once it rolled off the machine!)
I think, that´s a little bit from the tales and myths.
There was discussion on german forums when Mr. Rohloff decided to drop the chain production and afaik they stopped it due to the overwhelming varieties of different chain widths and specifications that were introduced with 9speed and 10speed drivetrains. It was too cost-intensive to adapt the self-designed and built chain assembly machine ("das Grüne Monster" / "the green monster") to the newer chain specs. The machine had built-in quality control, no need for Mr. Rohloff to sit beside the machine day and night.
I used the SLT-99 all the way through the nineties till 2009, when my last (second!) spare chain was worn and i couldn´t get a replacement any more at normal costs.
This was a damn-fine chain, it outperformed EVERY other brand even under harshest conditions. If you are interested, i have some photos of the "green monster" and an article about Mr. Rohloff and his products (of course in german) from a bike magazine bitd.
_________________Specialized RockHopper 1988 rebuild thread
Cannondale SM 2000 (1991)
, Specialized HardRock Cruz (1991), Specialized RockHopper Comp(1988)