Used night vision units are a crap shoot. You never know what it has been exposed to light and recoil wise. Both can damage a tube. I would never buy a used night vision device unless I thoroughly tested it and got it for less than half of what a new one goes for. At least with a new unit you have a 2-3 year factory warranty on the tube. You can get a new PVS14 OPMOD
with a gen 3 pinnacle tube for $2900, so anything over $1300-$1400 in my mind would be high.