I've done this once before. The jackets looked so damn similar, and were 1 size off.
I realized my mistake while the wrong package was in transit. I quickly emailed the buyer, informed him the first package arriving is incorrect, and the correct one is on its way. I told him as a token at my expense, he may choose to keep the first jacket at no cost, and do what he pleases with it (donate, gift, sell, dog chew toy)
He has since purchased over 10 other things from me since this has happened.
I think I've done this about 3 times just by mislabeling packages. Luckily, it has always been with lower value items and I've just refunded and told the person to keep the item in every instance but one (they guy was such a dick in his initial message that there was no way I was going to refund and let him keep it) . Especially if the items were thrifted, is it really worth the time and hassle, plus paying for return shipping?