Even the part numbers won't help -- these are several years old at this point, and anything could have happened to them in the interim.  Screens can easily be swapped. Go by the seller's description of the system - if you receive an HD screen described as FHD, return the system for replacement.  
HI All, I have a Latitude 5590 8th Gen with the Intel 620 UHD display adaptor but the maximum resolution I can get it to is 1366 x 768. I have all the latest drivers etc.... what am I doing wrong please?   I also have a Latitude 5590 7th Gen with the Intel 620 HD display adaptor and this goes to 1920 x 1080 without issue. In short - the newer laptop with the UHD driver is worse than the older laptop. Thanks
Latitude 5590 display won't go past 1366 x 768