Our 67 SJ GTA built 11-04-66 has as Bob described zinc plated single squriter type. Our 68 SJ HCS built 7-16-68 has the blackish finish double squirter type.
When I looked through my collection it appears that the black finish on the base wears off to leave a silver zinc finish. This could be a source of confusion particularly with photos.
I chose Marty's example to discuss because his build date is so close to mine 11/2/66 SJ vs. 11/4/66 SJ.
What I have found on my build is the "single squirter" with zinc plating ONLY on the mounting flange of the squirter nozzle. The tube portion was clearly a blackened color, much like the black rainbow-like finish we recently discussed on the 65-67 seat mounting shim plates.
This sounds inconsistent to what others are sharing but it appears like the blackened tubing was soldered on AFTER the plating of the mounting flange portion of this type of nozzle.
I sent both to be plated and now the whole nozzle is silver zinc, I feel unlike what it was originally. I did not exactly take a picture of the " before/after" except by cropping out images of the before but you can get an idea of an "all zinc" version of the "after" plating.