AFAIK, none of the original E9 LSD's had the external vent/reservoir, except those modified by people like Alpina (who had an optional oil pump driven off the output flange to circulate to a cooler for racing). Some of the E9 LSD's may not have been marked with the "S" on the outside (or it wore off). Retrofitting the later vent and external reservoir from an E24 or E12 is common. I agree that it's functionally meaningless for street driving but it's cool to have people lay on the ground so you can point it out at a cars and coffee event. For circuit racing, it's VERY helpful because the majority of the time you're on corners and the poor diff is heating up whether or slowing or accelerating.But are you saying that some side-loader differentials in the e9 cars have lsd but it’s not visible because there is no external reservoir and tube
John