Jeff, the zinc dichromate is what I personally have seen before in cars ,junkyards etc. with remnants of the gold . When the gold wears off it is silver and may be a source of possible mis identification on a FMX arm. As a side note the C6 rods are zinc dichromate too. I think the C6 ones are more commonly seen and have been documented more. I think that since the C6 ones were Zinc dichromate it would stand to reason that the FMX ones would not be any different. Of course there is always a possibility of a variation difference . I will continue to do more checking for variations but at the very least I am confident the gold was one of plating colors on the FMX arm .Just my opinion.