You cannot verify if it's a genuine Apple part for the following reason: There are replacement parts out there that were going to be genuine Apple parts, but eventually failed QC and were supposed to be destroyed. Some are being sold instead. That means you could get a part that would pass all possible checks, have the Apple logo and original serial numbers on there and whatnot - except that it still isn't "original" because Apple didn't accept it in the first place.
That is a problem with displays epecially because some come with issues from the factory to Apple Stores and are checked during a device repair in the store and then rejected on the spot. To give you an example, if you bring in an iPhone for display replacement the store will install a new original Apple part and then find out that the panel exhibits ghosting issues, discard that part, and repeat the repair.
So even if you were to get an original part, there are no guarantees that it lives up to specifications. Unlike Apple, you won't have a box full of original display panels where you can just discard a bad one and try again.
tl;dr it's a lottery what replacement part quality you get. The only guaranteed way to get a flawless and original Apple part is through a repair by Apple.