Wattle development at 5-6 weeks is concerning.
I’ve never had Orpingtons so I don’t know for sure but females don’t usually get that until after 8 weeks and usually much later.
One of my Silver Penciled Rocks has started developing some but she’s 10 weeks old.
Here’s Oliver, my black Australorp, at almost 5 weeks:
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At exactly 5 weeks:
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Here’s Oliver with one of the Silver Penciled Rocks, I think it’s Silver the older one. She’s the same age as Oliver.
Notice how there’s no comb or wattle development or color in her.
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And here he is at 7 weeks:
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Don’t panic. There’s nothing you can do about it.
I believe you said the seller would take him back if he turned out to be a cockerel?
You could keep him for a while yet.
Typically they don’t start crowing until about 3-4 months old.