Seller who are selling aging test DSis also seem to have a lot of 3DSs.
I saw that he posted a test prototype O3DS XL. (Its price is really low right now, those 3DS buyers are usually more greedy, and I think it'll be monopolized soon.)
I think it’s also used for factory testing, probably in large quantities.
Actually learned you can reuse some of those essential oil wick by yanking out the wick with the old plug and inserting the new oil/wick in the old container if it screws in better chance for a secure fit.