I'm trying to identify where this extended cut is to be found.
It was recorded from a french radio show on a cassette in the late 70's.
It's a better extended mix than the Island one. But I can't find any clue for that particular release.
After listening to your sample, I have the same version on a white label 12". It has a stamp on the label saying 'Sound System' and no other info. I bought it from a 2nd hand shop a few years ago. The matrix no. on it is WIP 6490 which according to RKR is the same as the Island issue. The b-side is Babylon Makes The Rules which is also the same as the Island 12, so I guess its an Island promo release.
I have a one-sided 12" with matrix 12XWIP 6490 and the words "Sound System" stamped on the label. Also someone has written "Steel Pulse Apr 79" on the label in felt tip pen. The B side of my copy is unplayable dead wax. I assumed that this was some kind of Island records promotional gimmick - that since the tune is titled Sound System, they try to make it look like a sound system dub plate.
After reading the initial post in this thread I dug it out and played it for the first time in years. I couldn't decide whether it was the same version as the sound sample provided by Nicholas - there are no easily discernable differences that I could hear.
Just picked up the one sided version yesterday...I need to dig out the standard 12" and compare...it didn't sound appreciably different on first listening but my memory could be playing tricks. Interesting that there is another stamped version with the Babylon b-side too though
Man, for me it was solved long time ago : the radio mix must have been a "custom extended mix" made from the Island 7", Sound System b/w Crampars Style. A complete different mix, way better than the 12" IMHO. These mixes were never re-issued AFAIK.