In the context of Blu-ray collecting, "solid paper" often describes premium packaging components:
: Includes an AVC encoded 1080p transfer in a 2.40:1 aspect ratio with English and Italian audio options. Collector's "Solid Paper" Elements Maze Runner Il Labirinto HD 2014 Bluray 1080p
Regarding "solid paper," this likely refers to the (or slipcase)—a decorative cardboard sleeve that fits over the standard plastic Blu-ray case. Release Details Title : Maze Runner - Il Labirinto (Italian Title) Format : Blu-ray (1080p FHD) Release Year : 2014 (Theatrical), early 2015 (Home Video) Studio : 20th Century Fox Home Entertainment In the context of Blu-ray collecting, "solid paper"
The Maze Runner Blu-ray 2014 DVD + Digital HD Action Sci-Fi - eBay In the context of Blu-ray collecting
The (2014) Blu-ray release in Italy typically refers to the high-definition 1080p presentation of the film, which was released in early 2015.