The backs can be deceptive. Try looking around the sides for a join, rather than at the back itself.
A picture of the electronics cavity would also help but the best way to be sure is to look under the pickups. You'll need to check for handwritten markings, the type of neck joint, and whether the maple joint and grain lines line up with the surface of the top.
I feel that a shop or a seller who paid the money for a 150 or above would most likely know exactly what they were getting and pass that information on when they sold it. They are not common and not many stores carry them on the shelves. It could still be an LS150 but with no fret edge binding I suspect it's an LS95F (page 21). This would have a neck joint that doesn't extend under the pickups, and the laminate top would mean the grain lines and maple cap joint wouldn't line up when you look into the pickup cavity towards the bridge.