[cctalk] what is it? 3850 stuff

Got this on eBay. 7 3850 cartridges, a piece of mag tape and some metal device in a nice box. I am trying to determine what the metal thing is. Some kind of alignment tool? For cartridge insertion in MSS unit, not track alignment? https://www.myimagecollection.com/whatisit/pic1.jpg https://www.myimagecollection.com/whatisit/pic2.jpg