45 rpm plastic insert adapter. Also known as a spider.
“45” RPM automatic spindle adapters. From Wikipedia
A site after Obso’s heart has already captured all the specs about patents and whatnot. “It appears that the molded plastic insert was invented by James L. D. Morrison for the Voice of Music corporation of Benton Harbor, Michigan.” Head over there for more.
Status: Bundle together as bonus with 45s that will be sold.
Kill-ratio: 26: 2/ 13: 1
Alt-title: Untitled Object No. 305 For Making Space For Sound.
Obsolescence Project 
…never knew they were called spiders.
i just gave some 45’s to a colleague who bought a jukebox… most of the spiders were missing