Download image from LOC. Sell cheap reprint on eBay. Receive order (maybe). Print and ship for a couple of dollars. Pocket difference. No sale? No real cost.
No disrespect intended, seller might not even be aware of the irony. Not the kind of biz I'm interested in, but if the image is out of copyright (not all images in the LOC are in the public domain - this one is listed as 'rights status not evaluated') it's legit.