Can airpods pro have this kind of engraving?

I won a box of sealed airpods pro at a quizz in a museum. I didn't need them so I sold them on eBay. The buyer told me that they were engraved. He sent me the picture below. He asked me for $30 refund. I checked on Apple web site what characters I could engrave, but it didn't accepte the > or < signs. Also, the engraving seems to be only on the box, but not on the buds themselves. So I'm wondering if maybe, the buyer put some sticker on it, in order to get a partial refund. I won these airpods pro last summer.

Please let me know what you think.