This thread has run its course now.
I have now worked out how this happens despite DH obviously caring deeply for me. And yes he does care deeply for me despite what the thread "mean girls" would like to project.
It has to do with salience, possibly related to neurodivergence. He knows nothing about jewellery but knows I like it, so wants to buy it for me. He goes to John Lewis every time because he thinks it sells decent stuff now we are no longer poor (neurodivergence again?) He remembers the cost and the type of item more than the specifics. Then he goes through the same thoughts process (I want to spend x amount, I like silver, I know she likes blue) and he ends up at similar items.
I can see how it would happen when I think about the laptops we buy for a particular milestone birthday for each child. That is his department. I know nothing about memory size, hard drive, etc etc. I would remember that we had bought each child "a laptop" but I would not recall any of the additional specification details. Theoretically, if they asked for a laptop upgrade and I was going to buy them another (this is theoretical, we do not do this, before I get 20 replies about how we spoil our kids) I would have zero recollection of the specification of the laptop or really it's appearance. It's just a laptop to me. I honestly believe that this is what is happening with Dh. He doesn't recall the jewellery "specification". So he buys the same one by accident because he sees me in the same way; a hippy girl with Indian skirts and wild hair who wears silver and blue.
I understand that sometimes people have partners who don't care about them. I am lucky not to be in that situation. Our relationship has not always been sweetness and light. We have had our ups and downs. But we are in a genuinely good place. If it had been obvious that he didn't care about me, I wouldn't have been baffled by the repeat earrings and would, like many on this thread, have ascribed it to a lack of care. However that is simply not the case.
We are off on holiday together, just the two of us, in a few days at his instigation. For my birthday as well as the earrings he bought me a weekend away with him. He actively wants to spend time with me, and we are happy.
i don't expect to be back on this thread now. Thanks to those people who haven't tried to batter me into interpreting my husband as a heartless monster who doesn't love me. It is simply not true.
Finally, my sister is just my sister; not a sock. I actually joined mumsnet many years ago at her recommendation. Love you @HumanBurrito and see you very soon! Xxx