Custom van seats from an aftermarket van converter. They may be Flexsteel, a popular brand, but could be anything. Try matching them at discountvantruck.com
Otherwise, you'd probably have to ask the seller to poke around and find you a name or tag under them. Good luck with that if it's your average Craigslist seller. If it's local you might be able to just look at them in person and figure it out yourself.
2010 Chevy AWD home build