Horizon Zero Dawn - Death Stranding Easter Egg (All Stranded Item Locations)

In HZD you can find 3 items from Kojima Production's Death Stranding E3 2016 reveal trailer and TGA 2016 teaser trailer. You can then trade them in at the speciality merchant in Meridian City. He gives you a mysterious box that contains a purple weapon mod and a very weird resource item called "Warm Socks".
The purose of the socks is still unkown. They can be sold for 100 Metal Shards at merchants, but perhaps they lead to another easter egg or a hint for upcoming announcements from Kojima Productions. Surely, there must be some meaning behind them but it could be a while before we find out.

Stranded Items Easter Egg Locations:

*You can return to all of these locations after finishing their respective missions and even in free roam after the story. They are inaccessible until you have completed the main quests listed below / during the video.

#1 - Stranded Necklace (worn by Norman Reedus in E3 2016 reveal trailer)
It's found in main quest "The Grave-Hoard". It's also marked on the map under the same name. Upon entering this area head to the far left of the room and jump over the broken machines. The necklace is on a corpse. Before sliding down the rope.

#2 - Stranded Shackles (on wrist of Norman Reedus in E3 2016 reveal trailer)
Found in main quest "Deep Secrets of the Earth", at the very end of the quest. It's easier if you return after the quest. Put on the Shadow Stalwart outfit and go to the map location marked as "Zero Dawn Alternate Entrance" (north-west in the desert). After entering turn to your right and it's sitting on a table close to the entrance.

#3 - Stranded Figure (doll that's swimming in the water during The Game Awards 2016 teaser trailer)
During main quest "The Heart of the Nora". After opening the big door in All-Mother it's under the first set of stairs.

Again, you can get all of these at any time after completing the missions!

Once you have all 3 stranded items visit the Speciality Merchant in Meridian. Trade him the items for the Mysterious Box and then open the box in your inventory.

Bonus fact: The inventory icons of the three stranded items look like the Kojima Productions logo.