I believe, based on part numbers and tape, that my speedo cable is original. I think the clip is too, but definitive proof -- no.
I went out to the parts car built the same week in SJ to see what it had but since it's a C4 it routes differently. However, there is a factory hole under the speed cable through-hole. This would appear to indicate that SJ had plans for this hole and this clip may be that use on 4 speed cars.
I do try to use words like 'appear', 'think', etc since I am not the original owner and definitive proof is impossible. Even then ...