The find was announced on the Reddit forum r/retrogaming by user keytarin. According to his post, the game was found amongst a collection purchased from an ex-employee of Milton Bradley.
Keytarin posts that “My contact told me that this prototype was among an assortment of loose materials that came over to MB’s offices during the transition [after the purchase of GCE] and wound up unclaimed in his possession at some point. From what my contact has told me and referencing the copyright date on the game’s title screen, it appears this game was programmed at GCE before MB bought the company”
You can see a video of the gameplay and more information about the find here. Keytarin’s aim is to preserve the prototype and make a copy of the ROM available to Vectrex fans and video game historians.