@B.A. The prototypes include After Burner II, Forgotten World, Castle of Illusion Starring Mickey Mouse (this is the Japanese version it seems), and Sonic the Hedgehog. There are three others that didn't run yesterday, but I will clean them and try different machines, etc. As @OptOut can personally attest, things are very wonky with the machines and tv I own, aside from my Famicom stuff, for unknown reasons of which we are trying to determine.
There was also a Ghouls n Ghosts and an Altered Beast in the set (not pictured). While on retail boards, the Ghouls n Ghosts chips code seem not to match any known Sega game, and the Altered Beast game seems to have early chip dates, so these might also be pre release games, though I'm not sure.