I agree Chippy is very likely a cockerel, but not sure why this is relevant? Iridescence isn't just a male thing.
I know both genders can have it.
I will try to explain why to me with chippy it is relevant.
Right now it is relevant because of Chippy's age. For this explanation I'm going to call Chippy a slower to mature cockerel.
Chippy should be going through one of his many juvenile molts. In my experience it is at this age range, 6 to 8 weeks that the sneaky males reveal themselves. They may not have the huge combs and wattles yet. They may not be early crowers, but the 6 to 8 week molts tend to reveal the males as male specific feathering and patterning comes in.
Now granted, my 2 speckled sussex were girls. What I have had though is countless Black Copper Marans cockerels. My hens were just that, boy moms so in my explanation I'm going to refer to them as I had several sneaky boys who I thought may be girls until that molt.
The first 6 weeks all Black Copper Marans look alike. They look like little penguins at hatch. They feather out black with white wing feather at the base of the wings which they loose around the 6 to 8 week molts. Both sexes if they have the full copper neck markings also have the copper feathering pop in at this age. If the boys are not already sprouting a bright red comb and wattles they can trick you into thinking they are pullets.
What gives those males away is the sudden appearance seemingly overnight of a copper feather on their shoulders or their backs. Hens do not have copper markings anywhere else besides their necks. What also coincides with these male specific feather patterns is iridescence. Specifically in their tails, backs and along their wings. At 6 to 8 weeks the pullets while black do not shine. Their feathers are still dull in all light conditions.
Those same dull girls, 5 months on after a few more molts, yes in the right lighting they sparkle. It is just never that early.
Ok, stepping away from Marans and focusing back on Speckled Sussex. There is no gender specific feather pattern. Both sexes will have that lovely speckled look. Looking at pictures of roosters recently there is one difference. The males have the green tint to their tails and their wings. That is why spotting those 2 green spots on Chippy and that 1 lone curved tail feather at 6 weeks is significant to me on gender guess. Combine that with his comb and wattles leads me to 100% believe he is a late blooming cockerel.